Compositions and methods for the treatment and prophylaxis of surgical site infections

ABSTRACT

The present invention provides methods for preventing, inhibiting or treating a surgical site infection associated with a surgical operation comprising the step of applying to the surgical site a biocompatible, biodegradable substrate being impregnated and/or having its surface coated fully or partially with a matrix composition which provides local controlled and prolonged release of at least one pharmaceutically active agent at the surgical site.

This application claims the benefit of U.S. provisional application No.62/058,809, filed Oct. 2, 2014 and entitled “COMPOSITIONS AND METHODSFOR THE TREATMENT AND PROPHYLAXIS OF SURGICAL SITE INFECTIONS”, thecontents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to sustained releasecompositions and uses thereof for the prevention and treatment ofsurgical site infections.

BACKGROUND OF THE INVENTION

Surgical site infection (SSI), an infection at or near surgicalincisions within 30 days of an operative procedure, is acommonly-occurring healthcare-associated infection, accounting for 15%of all nosocomial infections and, among surgical patients, representsthe most common nosocomial infection. Increased morbidity and mortalityare associated with SSI, ranging from wound discharge associated withsuperficial skin infection to life-threatening conditions such as severesepsis. SSIs are responsible for an increased economic burden tohealthcare systems, including additional postoperative hospital durationand costs.

The onset of a surgical site infection is caused by contaminants thatexist in the operative fields and are resistant to administeredantimicrobial agents. In the majority of SSI cases, the pathogen sourceis the native flora of the patient's skin, mucous membranes, or hollowviscera. When skin is incised, underlying tissue is exposed to overlyingendogenous flora. Staphylococcus aureus is a commonly-isolated organismin SSI, accounting for 15-20% of SSI occurring in hospital; otherorganisms regularly isolated from SSIs include gram-negative bacilli,coagulase-negative staphylococci, Enterococcus spp., and Escherichiacoli. Methicillin-resistant S. aureus (MRSA) is an increasinglyimportant pathogen that causes more than 50% of S. aureushospital-acquired infections in the US and Europe, and presentschallenges to treatment due to multiple antibiotic resistance. Yeastspecies and viral pathogens also pose a risk.

Surgical site infections present a significant clinical problem inorthopedic surgeries, spinal surgeries, operation of the digestivesystem, cardiac surgeries, breast operations and many other clinicalprocedures involving skin incision. For example, a serious complicationafter cardiac surgery with high morbidity and mortality rates reaching40% is sternotomy wound site infection (Mediastinitis). Patients withSternal wound infection require longer hospital stay, repeated surgicalinterventions, long-term antibiotic treatment, a substantial damage tothe quality of life, and great suffering to the patient. The cost oftreatment and financial burden in these patients for the health systemsis estimated to be 3-time-fold compared to patients undergoing opencardiac surgery, without any developed infection.

Typically colonization of surgical sites with biofilm makes themresistant to both antimicrobial as well as other interventions such assurgical debridement aimed at treating wound infection. Indeed, inrecent years, despite the development of new surgical techniques, newantibiotics, new technologies for postoperative infection diagnosis, andwound care technologies, the occurrence of surgical site infections hasnot been reduced.

International Publication No. WO 2010/007623 to one of the inventors ofthe present invention and others, the contents of which are incorporatedherein by reference, discloses drug delivery compositions for controlledrelease of an active ingredient, comprising a lipid-based matrix with abiodegradable polymer. These drug delivery compositions enable to entrapa large variety of one or more biologically active molecules and torelease them at a pre-programmed rate for periods ranging from severaldays to several months.

International Publication No. WO2014/020610 to the inventor of thepresent invention, the contents of which are incorporated herein byreference, discloses compositions, methods and medical devices for thetreatment of bone voids and bone defects comprising the step of applyingto a bone void or bone defect site a composition comprising a matrixwhich provides local prolonged release of at least one antibiotic agentat the bone void site.

Surgical site infections are still a major problem of the health caresystem. There is a need in the field for treatments to prevent and treatsurgical site infections locally at the surgical site.

SUMMARY OF THE INVENTION

The present invention provides methods for preventing, inhibiting ortreating a surgical site infection associated with a surgical operationcomprising the step of applying to the surgical site a biocompatible,biodegradable substrate being impregnated and/or having its surfacecoated fully or partially with a matrix composition which provides localcontrolled and prolonged release of at least one pharmaceutically activeagent at the surgical site. Specifically, the matrix compositioncomprises (a) a biocompatible polymer, (b) a first lipid componentcomprising a sterol, (c) a second lipid component comprising at leastone phospholipid having fatty acid moieties of at least 12 carbons; and(d) a pharmaceutically active agent selected from the group consistingof an antibiotic agent, antiseptic agent, an anti-inflammatory agent,anti-fungal agent and any combination thereof.

The substrate being impregnated and/or having its surface coated fullyor partially with a matrix composition described herein is intended forlocal administration to soft tissues and solid organs during surgicalprocedures and provides localized infection prevention and treatment byreducing the overall infection rate post-surgery and by reducing oreradicating soft tissue infections that may exist prior to surgery.According to some embodiments, the drug coated substrate describedherein prevents or inhibits the formation of biofilm that may form atthe surgical site and its vicinity, thereby preventing or inhibitingsurgical site infections. Inhibition of biofilm formation at thesurgical site refers to inhibition of biofilm formation on surfaces suchas biological tissues and/or materials or devices that may be usedduring surgery (e.g. wound tissue, necrotic cells, biomaterials andsurgical implants (e.g. sutures and hard ware-stainless steel wires)).According to some embodiments, the drug coated substrate disclosedherein is capable of eradicating an existing biofilm.

Following its application to the surgical site, the substrate beingimpregnated and/or having its surface coated fully or partially with amatrix composition described herein provides local controlled release ofthe drug at the surgical site and its surrounding over a predetermined,prolonged period of time, preferably between several days to severalweeks, thereby preventing or eradicating tissue infection.

The substrate impregnated or coated fully or partially with the matrixcomposition according to some embodiments of the invention, ispreferably administered to a subject that has or is at risk ofdeveloping an infection, prior to or during a treatment of the subjectwith a process that may cause infection and/or the formation of abiofilm in the subject. According to some embodiments, such process maybe any surgical procedure such as orthopedic surgical operations (e.g.hip arthroplasty, knee arthroplasty, total joint replacement, trauma),spine surgical operations, surgical operations on a digestive systemorgan (e.g. esophagus, stomach, small intestine, large intestine,rectum, colon, appendix, liver, pancreas, gallbladder, gastric ulcer,gastric cancer procedures, open gastric bypass, appendectomy, colectomy,cholecystectomy, vagotomy, open billary tract procedures, smallintestine procedures, colorectal procedures), cardiac procedures (e.g.coronary artery bypass, cardiothoracic transplantation procedures,cardiac device insertion procedures), hernia repair, vascularprocedures, caesarian, prostatectomy, obstetric and gynecologic surgicaloperations (e.g. hysterectomy), head and neck cancer surgery,transplantation surgeries (e.g. lung, liver, pancreas, kidney),neurosurgery (e.g. deep brain stimulation implant) and plastic surgeries(e.g. breast reconstruction, mastectomy).

The methods for preventing or inhibiting surgical site infections areuseful for preventing or inhibiting postoperative infection incontaminated or potentially contaminated surgery, wherein thepostoperative infection may be any one of a superficial incisionalinfection, a deep incisional infection and an organ/space infection.Also disclosed are methods for treating surgical site infectionsincluding preoperative, intraoperative and/or postoperative infections.Said pre-operative and/or postoperative infections may be associatedwith biofilm formation. Pre-operative infection may involve a biofilmformed in connection with a disease or condition in an organ, tissue orbody system (e.g. bone, skin, abdomen, urinary tract etc.). Such diseaseor condition may be selected, for example, from medical device relatedinfections, orthopedic implant infection, biliary stents andcatheter-related infections.

The method for suppressing, preventing and the method for treatingsurgical site infection according to embodiments of the invention, maybe additional to standard procedures for reduction in the inoculum ofbacteria such as appropriate surgical site preparation, systemicpreventive antibiotics, cell based therapy, and enhancement of the hostby perioperative supplemental oxygenation, maintenance of normothermiaand glycemic control.

According to some embodiments, the present invention provides asubstrate being impregnated or having its surface coated fully orpartially with a matrix composition comprising (a) a biocompatiblepolymer, (b) a first lipid component comprising a sterol which isnon-covalently associated with the biocompatible polymer, (c) a secondlipid component comprising at least one phospholipid having fatty acidmoieties of at least 12 carbons; and (d) at least one of an antibioticagent, an antiseptic agent, an anti-inflammatory agent, an anti-fungalagent or any combination thereof, said coated substrate is suitable forlocal administration to a surgical site and is capable of preventing ortreating surgical site infections. According to some embodiments, thematrix compositions provide sustained release of the pharmaceuticallyactive agent at the surgical site.

According to some embodiments, the substrate used in compositions andmethods described herein is a bioabsorbable hydrophilic material, whichhas biocompatibility (that is, is low in toxicity, shows only lowforeign body reactions in the living body, and may have a good affinitywith the body tissue), bioabsorbability (that is, biodegradability), andhydrophilicity, but which has low solubility in water or is insoluble inwater, and further has a solid shape at ambient temperature andformability. Any materials having these properties may be used withoutlimitation. The bioabsorbable hydrophilic materials according to someembodiments of the invention include mineral substrates, naturalpolymeric substrates and synthetic derivatives thereof. Non-limitingexamples of mineral substrates include hydroxyapatite, fluorapatite,oxyapatite, wollastonite, apatite/wollastonite glass ceramics,anorthite, calcium fluoride, calcium sulfate, calcium carbonate,tetracalcium phosphate, α-tricalcium phosphate (α-TCP), β-tricalciumphosphate (β-TCP), amorphous calcium phosphate, dicalcium phosphate,agrellite, devitrite, canasite, phlogopite, monetite, brushite,octocalcium phosphate, whitlockite, cordierite, berlinite, combeite,phosphoric acid crystals, disodium hydrogen phosphate, and otherphosphate salt-based bioceramics. Non-limiting examples of naturalpolymeric substrates include gelatin, hyaluronic acid, hyaluronic acidderivatives, such as, a polyionic complex of hyaluronic acid,triethanolamine alginate, casein, keratin, myosin and/or fibroin,collagen, collagen derivatives, such as, succinylated collagen ormethylated collagen, chondrotin sulfate, chitosan, chitosan derivatives,such as, methylpyrrolidone-chitosan, polyaminogalactosamine. Accordingto some embodiments, the substrate is a water-soluble synthetic polymersuch as for example poly vinyl alchohol (PVA), poly vinyl pyrrolidone(PVP), poly acrylic acid (PAA), N-(2-Hydroxypropyl) methacrylamide(HPMA), Poly(2-alkyl-2-oxazolines), polyphosphoesters (PPE),polyphosphates, and polyphosphonates. According to certain embodiments,the substrate is poly vinyl alchohol (PVA). According to someembodiments, the substrate is a bioabsorbable hydrophobic material, suchas for example a biodegradable polyester selected from the groupconsisting of PLA (polylactic acid), PGA (poly glycolic acid), PLGA(poly (lactic-co-glycolic acid)) and combinations thereof.

In some embodiments, the substrate is dense. In some embodiments, thesubstrate is porous. In some embodiments, the substrate is shaped in theform of particles (or granules). The substrate particles are typicallyspherical or steroidal. In some embodiments, the substrate particles,which need not be spherical and/or steroidal but preferably arespherical and/or spheroidal, may have an average diameter of for exampleat least about 30 μm, at least about 40 μm, at least about 50 μm, atleast about 60 μm, at least about 70 μm, at least about 80 μm, at leastabout 90 μm, at least about 100 μm, between 50 μm and 200 μm, between 50μm and 180 μm, between 70 μm and 150 μm and between 80 μm and 120 μm,between 50 μm and 100 μm and between 70 μm and 100 μm, not more thanabout 500 μm, not more than about 400 μm, not more than about 350 μm,not more than about 300 μm, not more than about 250 μm, not more thanabout 200 μm, not more than about 180 μm, not more than about 150 μm,not more than about 140 μm, not more than about 130 μm, not more thanabout 120 μm, not more than about 110 μm, not more than about 100 μm.According to some embodiments, the substrate particles are in the formof a powder. According to some embodiments, the substrate may be of anyshape (e.g. a sponge, net, sheet or fiber). It is appreciated by the oneskilled in the art, that the shape and/or size of the substrate may beadjusted, before or after coating or impregnating with the matrixcomposition, according to need (e.g. type, size and location ofincision). Each possibility represents a separate embodiment of theinvention.

In some embodiments, the biocompatible polymer in the coating matrixcomposition comprises a polyester selected from the group consisting ofPLA (polylactic acid), PGA (poly glycolic acid), PLGA (poly(lactic-co-glycolic acid)) and combinations thereof. According to someembodiments, the biocompatible polymer constitutes 5-30% of the matrix.According to some embodiments, the biocompatible polymer is polyethyleneglycol (PEG), preferably PEG having molecular weight of up to 10,000Dalton inclusive.

According to particular embodiments the first lipid comprises at leastone sterol. In some embodiments, the sterol is a phytosterol. In someembodiments, the sterol is a zoosterol. According to specificembodiments, the sterol is a cholesterol. In some embodiments, the firstlipid component comprises a mixture of sterols. In some embodiments, thefirst lipid component is substantially free of non-sterol lipids. Insome embodiments, the first lipid component constitutes 5-40% (w/w) ofthe matrix. In some preferred embodiments, the sterol is cholesterol andconstitutes up to 50% (w/w) of the total lipid content of said matrixcomposition. Total lipid content refers to total mass of all the lipidsin the matrix composition. for example, first lipid component, secondlipid component and any additional lipid additive comprised in thematrix composition. According to particular embodiments the first lipidand polymer are non-covalently associated.

In some embodiments, the fatty acid chains of the phospholipid containsat least 12 carbon atoms each. In some embodiments, the fatty acidchains of the phospholipid contains no more than 18 carbon atoms each.In some embodiments, the fatty acid chains of the phospholipid are fullysaturated. In some embodiments, at least one of the phospholipid fattyacid chains is non-saturated (e.g. contains at least one double bond).In some embodiments, both phospholipid fatty acid chains arenon-saturated. In some embodiments the second lipid comprises aphospholipid selected from the group consisting of aphosphatidylcholine, a mixture of phosphatidylcholines, aphosphatidylethanolamine, and combinations thereof. According to someembodiments the second lipid comprises a mixture ofphosphatidylcholines. According to some embodiments the second lipidcomponent further comprises an additional phospholipid selected from thegroup consisting of a phosphatidylserine, a phosphatidylglycerol, and aphosphatidylinositol. In some embodiments, the second lipid componentconstitutes 30-80% (w/w) of the matrix composition.

In some embodiments, the pharmaceutically active agent is incorporatedinto the matrix composition. According to certain embodiments, thepharmaceutically active agent is an antibiotic agent. According tocertain embodiments, the pharmaceutically active agent is an antisepticagent. According to certain embodiments, the pharmaceutically activeagent is an anti-inflammatory agent. According to certain embodiments,the pharmaceutically active agent is a steroid or a non-steroidalanti-inflammatory drug.

According to some embodiments, the pharmaceutically active agentconstitutes 1-20% (w/w) of the matrix composition. According to someembodiments, the pharmaceutically active agent constitutes about 5-15%(w/w) of the matrix composition. According to certain typicalembodiments, the pharmaceutically active agent constitutes about 8-12%(w/w) of the matrix composition.

According to some embodiments, the coated substrate used for preventingand/or treating surgical site infections constitutes between about60-90% (w/w) of substrate and 10-40% (w/w) of the matrix compositiondescribed herein. According to some embodiments the coated substrateconstitutes between about 70-90% (w/w) of substrate and 10-30% (w/w) ofthe matrix composition. According to some embodiments the coatedsubstrate constitutes between about 80-90% (w/w) of substrate and 10-20%(w/w) of the matrix composition. According to some embodiments thecoated substrate constitutes between about 85-90% (w/w) of substrate and10-15% (w/w) of the matrix composition.

In some embodiments, the coating matrix composition has a highlyorganized multilayer structure in which the polymer and lipids areorganized in the form of multiple alternating layers. According to someembodiments, the matrix composition comprises a continuous structuredevoid of internal gaps and/or free volume. According to someembodiments, the matrix composition is lipid saturated indicating thatthe space between the polymer layers or polymer backbone is filled withlipid molecules in combination the pharmaceutical agent, to the extentthat additional lipid moieties can no longer be incorporated into thematrix to an appreciable extent.

In some embodiments, the matrix composition is capable of releasing atleast 30% of the pharmaceutical agent at zero-order kinetics. Withoutbeing limited by a specific theory or mechanism of action it issuggested that this organized structure or substructure of the matrixcomposition of the invention is one of the main reasons for thezero-order release rate of the drug or drugs from the matrix formulationfollowing its hydration. Thus, the zero order release rate may beattributed to slow and continuous “peeling” of drug together with theformulation components from the hydrated surface layer(s) of the highlyorganized layers of lipids and polymer. According to some embodimentsthe matrix of the present invention is water resistant. As such watercannot easily, if at all, diffuse into the matrix and thepharmaceutically active agent entrapped between the layers cannoteasily, if at all, diffuse out of the matrix. According to someembodiments, the drug is being released from the matrix compositionsdisclosed herein upon the gradual surface degradation of the matrix,thus enabling extended release ranging from several days to severalweeks. The biocompatible substrate itself preserves its threedimensional structure over the course of pharmaceutical agent releasedue to the hydrophobic matrix composition that coats or impregnates thesubstrate. Gradual degradation of the matrix composition which willeventually lead to exposure of the substrate's surface. Exposure of thebiodegradable substrate to body fluids will initiate its degradation andremoval, leaving no traces at the treated surgical site. In a particularembodiment, the present invention provides methods for suppressing,preventing or treating a surgical site infection associated with asurgical operation comprising the step of applying to the surgical sitea biodegradable substrate being impregnated and/or having its surfacecoated fully or partially with a matrix composition comprising: (a)biodegradable polyester; (b) a sterol; (c) a phosphatidylcholine havingfatty acid moieties of at least 14 carbons; and (d) an antibiotic agent.In another embodiment, the matrix composition comprises at least 50%lipid by weight of the matrix. In another embodiment, matrix compositioncomprises at least 40% phospholipids by weight of the matrix. In someembodiments, the biodegradable, slow release coating formulationcomprises at least 10% polymer by weight of the matrix. In someembodiments, the biodegradable, slow release coating formulation(matrix) comprises at least 5% antibiotic by weight of the matrix. Inanother embodiment, the matrix composition is homogeneous. In someembodiments, the polymer, sterol non-covalently associated therewith,and the phospholipid form a structurally ordered lipid-saturated matrixcomposition that is substantially free of water. According to certainembodiments, the substrate coated/impregnated with the matrixcomposition is selected from tri-calcium phosphate particles orpolyvinyl alcohol particles.

According to some embodiments, the matrix composition comprises: (a) abiodegradable polyester selected from PLA, PGA and PLGA; (b) cholesterolwhich is non-covalently associated with the biodegradable polyester; (c)at least one phospholipid having fatty acid moieties of 16-18 carbons;and (d) an antibiotic agent. In another embodiment, the matrixcomposition comprises at least 50% lipid by weight of the matrix. Inanother embodiment, matrix composition comprises at least 40%phospholipids by weight of the matrix. In some embodiments, thebiodegradable, slow release coating formulation comprises at least 10%polymer by weight of the matrix. In some embodiments, the biodegradable,slow release coating formulation (matrix) comprises at least 5%antibiotic by weight of the matrix. In some embodiments, thephospholipid is a phosphatidylcholine. In some embodiments, thephosphatidylcholine is a mixture of phosphatidylcholines. In someembodiments the phosphatidylcholine(s) have saturated fatty acidmoieties, i.e. no carbon-carbon double bonds in the fatty acid chains.In some embodiments, the phospholipid is selected from the groupconsisting of DMPC, DPPC, DSPC, DOPC and any combination thereof. Insome embodiments, the phospholipid is selected from DPPC, DSPC and anycombination thereof. In some embodiments, the phospholipid is selectedfrom DMPC, DPPC and any combination thereof. In some embodiments, thephospholipid is selected from DMPC, DPPC, DOPC and any combinationthereof. In some embodiments, the polymer, cholesterol associatedtherewith, and the phospholipid form a structurally orderedlipid-saturated matrix composition that is substantially free of water.According to certain embodiments, the substrate coated/impregnated withthe matrix composition is selected from tri-calcium phosphate particlesor polyvinyl alcohol particles.

According to some embodiments, the matrix composition comprises: (a)Poly ethylene glycol (PEG); (b) cholesterol which is non-covalentlyassociated with the polymer; (c) at least one phospholipid having fattyacid moieties of 14-18 carbons; and (d) an antibiotic agent. In anotherembodiment, the matrix composition comprises at least 50% lipid byweight of the matrix. In another embodiment, matrix compositioncomprises at least 40% phospholipids by weight of the matrix. In someembodiments, the biodegradable, slow release coating formulationcomprises at least 10% polymer by weight of the matrix. In someembodiments, the biodegradable, slow release coating formulation(matrix) comprises at least 5% antibiotic by weight of the matrix. Insome embodiments, the phospholipid is a phosphatidylcholine. In someembodiments, the phosphatidylcholine is a mixture ofphosphatidylcholines. In some embodiments the phosphatidylcholine(s)have saturated fatty acid moieties, i.e. no carbon-carbon double bondsin the fatty acid chains. In some embodiments, the phospholipid isselected from the group consisting of DMPC, DPPC, DSPC, DOPC and anycombination thereof. In some embodiments, the phospholipid is selectedfrom DPPC, DSPC and any combination thereof. In some embodiments, thephospholipid is selected from DMPC, DPPC and any combination thereof. Insome embodiments, the phospholipid is selected from DMPC, DPPC, DOPC andany combination thereof. In some embodiments, the polymer, cholesterolassociated therewith, and the phospholipid form a structurally orderedlipid-saturated matrix composition that is substantially free of water.According to certain embodiments, the substrate coated/impregnated withthe matrix composition is selected from tri-calcium phosphate particlesor polyvinyl alcohol particles.

The present invention provides a biodegradable substrate which isimpregnated and/or which has its surface coated fully or partially witha matrix composition which provides local controlled and prolongedrelease of at least one pharmaceutically active agent for use insuppressing or preventing a surgical site infection associated with asurgical operation. Specifically, the coating matrix compositioncomprises (a) a biocompatible polymer, (b) a first lipid componentcomprising a sterol, (c) a second lipid component comprising at leastone phospholipid having fatty acid moieties of at least 12 carbons; and(d) a pharmaceutically active agent.

The present invention further provides a biodegradable substrate whichis impregnated and/or which has its surface coated fully or partiallywith a matrix composition which provides local controlled and prolongedrelease of at least one pharmaceutically active agent for use intreating surgical site infection associated with a surgical operation.Specifically, the coating matrix composition comprises (a) abiocompatible polymer, (b) a first lipid component comprising a sterol,(c) a second lipid component comprising at least one phospholipid havingfatty acid moieties of at least 12 carbons; and (d) a pharmaceuticallyactive agent.

The present invention further provides a biodegradable substrate whichis impregnated and/or which has its surface coated fully or partiallywith a matrix composition comprising (a) a biocompatible polymer, (b) afirst lipid component comprising a sterol, (c) a second lipid componentcomprising at least one phospholipid having fatty acid moieties of atleast 12 carbons; and (d) a pharmaceutically active agent, for use inadministering said pharmaceutically active agent to soft tissues andsolid organs during surgical procedures of a subject in need thereof.

Further embodiments and the full scope of applicability of the presentinvention will become apparent from the detailed description givenhereinafter. However, it should be understood that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the accumulated release profile of doxycycline hyclate fromhydrated (5% serum at 37° C.) tri-calcium phosphate (TCP) particles(˜100 μm) impregnated with a matrix composition composed of PLGA,cholesterol, DPPC, DSPC and doxycycline hyclate.

FIG. 2 shows the accumulated release profile of doxycycline hyclate fromhydrated (5% serum at 37° C.) poly vinyl alcohol (PVA) particlesimpregnated with a matrix composition composed of PLGA, cholesterol,DPPC, DSPC and doxycycline hyclate, post hydration in 5% serum at 37° C.

FIGS. 3A, 3B, 3C and 3D show SEM images of uncoated globular PVAparticles having a porous rough terrain surface (FIGS. 3A and 3B,magnification ×500 and ×25000 respectively), and similar PVA particlesimpregnated with a matrix composition composed of PLGA, cholesterol,DPPC, DSPC and doxycycline hyclate (FIGS. 3C and 3D, magnification ×500and ×25000 respectively). FIGS. 3C and 3D show that both outer and innersurfaces of the particles are coated.

FIG. 4 shows the efficacy of tri-calcium phosphate granules (˜100 μm)coated with a matrix composition comprising doxycycline according tosome embodiments of the invention (“Test article”) in reducing bacterialproliferation following induction of a surgical site infection (SSI)model attained by intramuscular implantation of the Test articlecombined with Staphylococcus aureus in SD rats. Implantation of uncoatedTCP particles combined with Staphylococcus aureus served as control.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides methods for preventing or treating asurgical site infection associated with a surgical operation comprisingthe step of applying to the surgical site a biocompatible, biodegradablesubstrate being impregnated and/or having its surface coated fully orpartially with a matrix composition which provides local controlled andprolonged release of at least one pharmaceutically active agent at thesurgical site of a subject in need thereof. Specifically, the matrixcomposition comprises (a) a biocompatible polymer, (b) a first lipidcomponent comprising a sterol, (c) a second lipid component comprisingat least one phospholipid having fatty acid moieties of at least 12carbons; and (d) a pharmaceutically active agent selected from the groupconsisting of an antibiotic agent, antiseptic agent, ananti-inflammatory agent, anti-fungal agent and any combination thereof.

As used herein, the term “surgical site” refers to a site created by anyopening in the skin or internal organs performed for a specific medicalpurpose. A surgical site being “open” refers to surgical sites wheremedical personnel have direct physical access to the area of interest. Asurgical site may include, but is not limited to, organs, muscles,tendons, ligaments, connective tissue and the like.

The methods of the present invention are also suitable for the treatmentof open wounds. Open wounds as used herein refer generally to a bodilyinjury with disruption of the normal integrity of tissue structures andmore particularly to a type of injury in which skin is torn, cut, orpunctured. Open wounds include without limitation: Incisions or incisedwounds, lacerations, penetration wounds, septic wounds, burn injuriesetc.

As used herein, “preventing” or “prophylaxis” of surgical site infectionrelate to inhibiting or eradicating the replication of bacteria at thesurgical site and its surroundings, inhibit transmission of bacteria orpreventing the bacteria from establishing itself at the surgical siteand its surroundings, or alleviating the symptoms of a disease that maybe caused by infection. A treatment will be considered therapeutic ifthere is a reduction in bacterial load.

The methods according to some embodiments of the invention are suitablefor the prevention or inhibition of biofilm formation at the surgicalsite and its vicinity in a subject in need thereof. Inhibition ofbiofilm formation at the surgical site refers to inhibition of biofilmformation on surfaces such as biological tissues and/or materials ordevices that may be used or implanted during surgery. According to someembodiments, the drug coated substrate disclosed herein is also capableof eradicating an existing biofilm formed prior to the surgicaloperation.

The term “biofilm” is defined herein in accordance with its regularmeaning in the art as a structured community of microorganisms growingattached to a surface and producing a slime layer of extracellularpolymers in which the microbial consortia is embedded in a protectiveenvironment. The surfaces to which the biofilm is adherent to may beinert or living surfaces (e.g. wound tissue, necrotic cells,biomaterials and surgical implants (e.g. sutures and hard ware-stainlesssteel wires)). A biofilm community can include bacteria, fungi, yeastsprotozoa and other microorganisms. Biofilms that are commonly foundassociated with human tissue and organ surfaces are frequently bacterialbiofilms.

The “subject” as used herein refers to an individual, a patient, thathas infection, is developing an infection (biofilm formation isclinically evident or detectable to the skilled artisan, but has not yetfully formed), or is at risk of developing an invention (no biofilmformation is yet detectable to the clinician or skilled artisan, but thesubject is known to be at risk of developing a biofilm due to disease orthe pending performance of a surgical procedure, such as for example acardiac surgery or graft implantation). The term “subject” refers to amammal, preferably a human that is to be treated or is being treated bya clinician (doctor, nurse or other medical practitioner) for a disease,condition, procedure, or routine examination.

The term “controlled release” refers to control of the rate and/orquantity of pharmaceutically active agent(s) delivered by the matrixcompositions of the invention. The controlled release can be continuousor discontinuous, and/or linear or non-linear.

The term “sustained release” means that pharmaceutical active agent isreleased over an extended period of time.

General Characteristics of the Matrix Composition Used for SubstrateCoating

The matrix composition used for impregnating or coating a biodegradablesubstrate according to some embodiments of the invention comprises (a) abiocompatible polymer, (b) a first lipid component comprising at leastone sterol which is non-covalently associated with the biocompatiblepolymer (c) a second lipid component comprising at least onephospholipid having fatty acid moieties of at least 12 carbons; and (d)a pharmaceutically active agent. The matrix compositions providesustained release of the pharmaceutically active agent at a surgicalsite in the body of a subject in need thereof.

In specific embodiments, the polymer and the lipids form a structurallyordered lipid saturated matrix composition that is substantially free ofwater. In some embodiments, the matrix composition has a highlyorganized multilayer structure in which the polymer and lipids areorganized in the form of multiple alternating layers. In someembodiments, the biocompatible coating matrix comprises at least about50% total lipids by weight.

In some embodiments, the matrix composition comprises at least 10%biocompatible polymer by weight. In some embodiments, the matrixcomposition comprises between about 10-30% polymer by weight. In someembodiments, the matrix composition comprises between about 15-25%polymer by weight. In some embodiments the matrix composition comprisesabout 20% polymer by weight. In some embodiments the biocompatiblepolymer constitutes at least 10% (w/w), at least 11% (w/w), at least 12%(w/w), at least 13% (w/w), at least 14% (w/w), at least 15% (w/w), atleast 16% (w/w), at least 17% (w/w), at least 18% (w/w), at least 19%(w/w), at least 20% (w/w), at least 21% (w/w), at least 22% (w/w), atleast 23% (w/w), at least 24% (w/w), at least 25% (w/w), at least 26%(w/w), at least 27% (w/w), at least 28% (w/w), at least 29% (w/w), atleast 30% (w/w) of the matrix.

According to certain embodiments of the invention, the polymer is abiodegradable polyester. According to some embodiments the polyester isselected from the group consisting of PLA (polylactic acid). “PLA”refers to poly(L-lactide), (poly(D-lactide), and poly(DL-lactide). Inanother embodiment, the polymer is PGA (polyglycolic acid). In anotherembodiment, the polymer is PLGA (poly(lactic-co-glycolic acid). The PLAcontained in the PLGA may be any PLA known in the art, e.g. eitherenantiomer or a racemic mixture. The PLGA of methods and compositions ofthe present invention has, in another embodiment, a 50:50 lacticacid/glycolic acid ratio. In another embodiment, the ratio is 60:40. Inanother embodiment, the ratio is 75:25. In another embodiment, the ratiois 85:15. In another embodiment, the ratio is 90:10. In anotherembodiment, the ratio is 95:5. In another embodiment, the ratio isanother ratio appropriate for an extended or sustained in vivo releaseprofile. The PLGA may be either a random or block copolymer. Eachpossibility represents a separate embodiment of the present invention.It is to be emphasized that the polymer may be of any size or length(i.e of any molecular weight).

In another embodiment, the biodegradable polyester may be selected fromthe group consisting of polycaprolactone, polyhydroxyalkanoate,polypropylenefumarate, polyorthoester, polyanhydride, andpolyalkylcyanoacrylate, provided that the polyester contains a hydrogenbond acceptor moiety. In another embodiment, the biodegradable polyesteris a block copolymer containing a combination of any two monomersselected from the group consisting of a PLA, PGA, a PLGA,polycaprolactone, a polyhydroxyalkanoate, a polypropylenefumarate, apolyorthoester, a polyanhydride, and a polyalkylcyanoacrylate. Inanother embodiment, the biodegradable polyester is a random copolymercontaining a combination of any two of the monomers listed above. Eachpossibility represents a separate embodiment of the present invention.

The term “biodegradable” refers to a substance that will degrade overtime by hydrolytic action, by the action of enzymes and/or by othersimilar mechanisms in the human body. “Biodegradable” further includesthat a substance can break down or degrade within the body to non-toxiccomponents after or while a therapeutic agent has been or is beingreleased.

The term “Biocompatible” refers to a substance that will not causesubstantial tissue irritation or necrosis at the target tissue site.

According to some embodiments, the matrix composition comprises up to40% (w/w) of a first lipid component comprising a sterol which isnon-covalently associated with the biocompatible polymer. According tosome embodiments, the sterol constitutes up to about 30% (w/w) of theweight of the matrix composition. According to some embodiments, thematrix composition comprises about 5-40% (w/w) of a first lipidcomponent comprising a sterol. According to some embodiments, the matrixcomposition comprises about 5-30% (w/w) of sterol. According to someembodiments, the matrix composition comprises about 5-20% (w/w) ofsterol. According to some embodiments, the matrix composition comprisesabout 5-15% (w/w) of sterol. According to some embodiments, the matrixcomposition comprises about 7-13% (w/w) of sterol. According to someembodiments, the matrix composition comprises about 9-11% (w/w) ofsterol. According to certain typical embodiments, the matrix compositioncomprises about 10% (w/w) of sterol. In some embodiments the sterolconstitutes at least 5% (w/w), at least 6% (w/w), at least 7% (w/w), atleast 8% (w/w), at least 9% (w/w), at least 10% (w/w), at least 11%(w/w), at least 12% (w/w), at least 13% (w/w), at least 14% (w/w), atleast 15% (w/w), at least 16% (w/w), at least 17% (w/w), at least 18%(w/w), or at least 19% (w/w) of the matrix. In some embodiments, sterolconstitutes not more than 20% (w/w), not more than 19% (w/w), not morethan 18% (w/w), not more than 17% (w/w), not more than 16% (w/w), notmore than 15% (w/w), not more than 14% (w/w), not more than 13% (w/w),not more than 12% (w/w), not more than 11% (w/w), not more than 10%(w/w), not more than 9% (w/w), not more than 8% (w/w), not more than 7%(w/w), not more than 6% (w/w), or not more than 5% (w/w) of the matrix.According to some currently preferred embodiments, the sterol ischolesterol.

According to some embodiments, the matrix composition comprises at leastabout 30% (w/w) of a second lipid component comprising at least onephospholipid having fatty acid moieties of at least 12 carbons.According to some embodiments, the matrix composition comprises at leastabout 40% (w/w) of a second lipid component comprising at least onephospholipid having fatty acid moieties of at least 12 carbons.According to some embodiments, the matrix composition comprises about40-75% (w/w) of a second lipid component comprising at least onephospholipid having fatty acid moieties of at least 12 carbons.According to some embodiments, the matrix composition comprises about50-70% (w/w) of a second lipid component comprising at least onephospholipid having fatty acid moieties of at least 12 carbons.According to certain typical embodiments, the matrix compositioncomprises about 60% (w/w) a second lipid component comprising at leastone phospholipid having fatty acid moieties of at least 12 carbons. Insome embodiments, the second lipid component comprising at least onephospholipid having fatty acid moieties of at least 12 carbonsconstitute at least 40% (w/w), at least 45% (w/w), at least 50% (w/w),at least 55% (w/w), at least 60% (w/w), at least 65% (w/w), or at least70% (w/w), of the matrix. In some embodiments, the second lipidcomponent comprising at least one phospholipid having fatty acidmoieties of at least 12 carbons constitute not more than 75% (w/w), notmore than 70% (w/w), not more than 65% (w/w) of the matrix. According tosome embodiments, the second lipid component comprises at least onephospholipid molecule having fatty acid moieties of at least 14 carbons.According to some embodiments, the second lipid component comprises atleast one phosphatidylcholine molecules having fatty acid moieties of atleast 14 carbons. According to some embodiments, the phosphatidylcholinemolecules of the composition comprise DMPC. According to someembodiments, the phosphatidylcholine molecules of the compositioncomprise DPPC. According to some embodiments, the phosphatidylcholinemolecules of the composition comprise DSPC. According to someembodiments, the matrix composition comprises DOPC. According to someembodiments, the matrix composition comprises a mixture of DOPC with asecond phospholipid having fatty acid moieties of at least 14 carbons.According to some embodiments, the matrix composition comprises amixture of DMPC and DPPC. Typically the ratio between DMPC and DPPC inthe formulation is between about 10:1 to 1:10. According to someembodiments, the matrix composition comprises a mixture of DPPC andDSPC. Typically the ratio between DPPC and DSPC in the formulation isbetween about 10:1 to 1:1; preferably between 5:1 and 2:1; morepreferably the ratio between DPPC and DSPC in the formulation is about3:1. According to some embodiments, the matrix composition comprisesabout 50-70% (w/w) of a mixture of DMPC and DPPC. According to someembodiments, the matrix composition comprises about 50-70% (w/w) of amixture of DPPC and DSPC.

In some embodiments, the lipid:polymer weight ratio of a composition ofthe present invention is between 1:1 and 9:1 inclusive. In anotherembodiment, the ratio is between 2:1 and 9:1 inclusive. In anotherembodiment, the ratio is between 3:1 and 9:1 inclusive. In anotherembodiment, the ratio is between 4:1 and 9:1 inclusive. In anotherembodiment, the ratio is between 5:1 and 9:1 inclusive. In anotherembodiment, the ratio is between 6:1 and 9:1 inclusive. In anotherembodiment, the ratio is between 7:1 and 9:1 inclusive. In anotherembodiment, the ratio is between 8:1 and 9:1 inclusive. In anotherembodiment, the ratio is between 1.5:1 and 9:1 inclusive. Eachpossibility represents a separate embodiment of the present invention.

It is to be emphasized that the sustained release period using thecompositions of the present invention can be programmed taking intoaccount the biochemical and/or biophysical properties of the biopolymerand the lipid. Specifically, the degradation rate of the polymer and thefluidity of the lipid should be considered. For example, a PLGA (85:15)polymer will degrade slower than a PLGA (50:50) polymer. Aphosphatidylcholine (12:0) is more fluid (less rigid and less ordered)at body temperature than a phosphatidylcholine (18:0). Thus, forexample, the release rate of a drug incorporated in a matrix compositioncomprising PLGA (85:15) and phosphatidylcholine (18:0) will be slowerthan that of a drug incorporated in a matrix composed of PLGA (50:50)and phosphatidylcholine (14:0). Another aspect that will determine therelease rate is the physical characteristics of the entrapped orimpregnated drug. In addition, the release rate of drugs can further becontrolled by the addition of other lipids into the matrix formulation,some of which are described below.

According to some embodiments, the matrix composition comprises about1-20% (w/w) of the pharmaceutically active agent. According to someembodiments, the matrix composition comprises about 5-15% (w/w) of thepharmaceutically active agent. According to certain embodiments, thematrix composition comprises about 8-12% (w/w) of the pharmaceuticallyactive agent. According to certain embodiments, the matrix compositioncomprises about 10% (w/w) of the pharmaceutically active agent. In someembodiments, the pharmaceutically active agent constitutes at least 1%(w/w), at least 2% (w/w), at least 3% (w/w), at least 4% (w/w), at least5% (w/w), at least 6% (w/w), at least 7% (w/w), at least 8% (w/w), atleast 9% (w/w), at least 10% (w/w), at least 11% (w/w), at least 12%(w/w), at least 13% (w/w), at least 14% (w/w), at least 15% (w/w), atleast 16% (w/w), at least 17% (w/w), at least 18% (w/w), or at least 19%(w/w) of the matrix. In some embodiments, the pharmaceutically activeagent constitutes not more than 20% (w/w), not more than 19% (w/w), notmore than 18% (w/w), not more than 17% (w/w), not more than 16% (w/w),not more than 15% (w/w), not more than 14% (w/w), not more than 13%(w/w), not more than 12% (w/w), not more than 11% (w/w), not more than10% (w/w), not more than 9% (w/w), not more than 8% (w/w), not more than7% (w/w), not more than 6 (w/w), not more than 5% (w/w) of the matrix.

According to certain embodiments, the pharmaceutically active agent isan antibiotic agent. According to certain embodiments, thepharmaceutically active agent is an antifungal agent. According tocertain embodiments, the pharmaceutically active agent is an antisepticagent. According to certain embodiments, the pharmaceutically activeagent is an anti-inflammatory agent. According to certain embodiments,the pharmaceutically active agent is a steroid or a non-steroidalanti-inflammatory drug. In some embodiment, a plurality ofpharmaceutically active agents are incorporated into the matrixcomposition, for example, a combination of two or more antibioticagents, a combination of one or more antibiotic agents and one or moreantifungal agent, a combination of one or more antibiotic agents and oneor more non-steroidal anti-inflammatory drugs (NSAID). In someembodiments, the pharmaceutically active agent is incorporated into thematrix composition. Each possibility represents a separate embodiment ofthe present invention. According to some embodiments, thepharmaceutically active agent has low water solubility. In anotherembodiment, the pharmaceutically active agent is hydrophobic. In anotherembodiment, the pharmaceutically active agent is an amphipathic.

The term “hydrophobic” relates to a material, having solubility indistilled water at ambient temperature of less than about 1 gr per 100ml, or less than about 0.5 gm per 100 ml, or less than about 0.1 gm per100 ml.

A pharmaceutically active agent having low water solubility as usedherein, relates to a material having solubility in distilled water atambient temperatures of less than about 3 gr per 100 ml, or less thanabout 2 gr per 100 ml, between 1-2 gr per 100 ml.

According to some embodiments, the pharmaceutically active agent used inmethods according to some embodiments of the invention is an antibioticagent selected from the group consisting of penicillin antibiotics,cephem antibiotics, macrolide antibiotics, tetracycline antibiotics,glycycycline antibiotics, fosfomycin antibiotics, aminoglycosideantibiotics, and new quinolone antibiotics. Non-limiting examples ofantibiotic agents include amoxicillin, amoxicillin/clavulanic acid,ampicillin/sulbactam, penicillin, metronidazole, clindamycine,chlortetracycline, dcmeclocycline, oxytetracycline, amikacin,gentamicin, kanamycin, neomycin, netilmicin, streptomycin, tobramycin,cefadroxil, cefazolin, cephalexin, cephalothin, cephapirin, cephradine,cefaclor, cefamandole, cefametazole, cefonicid, cefotetan, cefoxitine,cefpodoxime, cefprozil, cefuroxime, cefdinir, cefixime, cefoperazone,cefotaxime, ceftazidime, ceftibuten, ceftizoxime, ceftriaxone, cefepime,azithromycin, claforan, clarithromycin, dirithromycin, erythromycin,lincomycin, troleandomycin, bacampicillin, carbenicillin, cloxacillin,dicloxacillin, meticillin, mezlocillin, nafcillin, oxacillin,piperacillin, ticarcillin, cinoxacin, ciprofloxacin, enoxacin,grepafloxacin, levofloxacin, lomefloxacin, nalidixic acid, norfloxacin,ofloxacin, sparfloxacin, sulfisoxazole, sulfacytine, sulfadiazine,sulfamethoxazole, sulfisoxazole, dapson, aztreonam, bacitracin,capreomycin, chloramphenicol, clofazimine, colistimethate, colistin,cycloserine, fosfomycin, furazolidone, methenamine, nitrofurantoin,pentamidine, rifabutin, rifampin, spectinomycin, tigecycline,trimethoprim, trimetrexate glucuronate, vancomycin, chlorhexidine andcarbapenem antibiotics such as ertapenem. According to some embodimentsthe antibiotic agent is an antibiotic peptide. Each antibioticrepresents a separate embodiment of the present invention.

According to some currently preferred embodiments, the antibiotic agentof methods and compositions of the present invention is a tetracycline.In one embodiment, the tetracycline is doxycycline. In anotherembodiment, the antibiotic is a hydrophobic tetracycline. Non-limitingexamples of hydrophobic tetracyclines are6-demethyl-6-deoxytetracycline, 6-methylene tetracycline, minocycline(also known as 7-dimethylamino-6-demethyl-6-deoxytetracycline), and13-phenylmercapto-a-6-deoxytetracycline. In another embodiment, theantibiotic is selected from the group consisting of doxycycline,tetracycline, and minocycline.

In another embodiment, the antibiotic is doxycycline or doxycyclinehyclate. Doxycycline can be effectively used for treating surgical siteinfections caused by many types of both Gram-negative and Gram-positivebacteria and is used for treating a number of conditions. Mostimportantly, Doxycycline is highly effective against Staphylococcusaureus (S. aureus), the most common bacteria causing surgical siteinfections. Furthermore, bacteriologic testing indicates appropriatesusceptibility to doxycycline by Methicillin-resistant Staphylococcusaureus (MRSA). The minimal inhibitory concentrations (MIC) ofDoxycycline against common bacteria, as well as such S. aureus arerelatively low, and can be as low as 0.1 μg/ml (for S. aureus), allowinghigh potency in vivo against surgical site infections.

According to some embodiments, the pharmaceutically active agent used inmethods according to some embodiments of the invention is an antifungalagent selected from the group consisting of amphotericin B cholesterylsulfate complex, natamycin, amphotericine, clotrimazole, nystatin,amphotericin B lipid complex, fluconazole, flucytosine, griseofulvin,itraconazole, ketoconazole, benzoic acid and salicylic acid,betamethasone and clotrimazole, butenafine, carbol-fuchsin, ciclopirox,clioquinol, clioquinol and hydrocortisone, clotrimazole, econazole,gentian violet, haloprogin, iodoquinol and hydrocortisone, ketoconazole,miconazole, naftifine, nystatin, nystatin and triamcinolone,oxiconazole, sodium thiosulfate, sulconazole, terbinafine, tolnaftate,triacetin, undecylenic acid and derivatives thereof, butoconazole,clotrimazole, sulfanilamide, terconazole, and tioconazole.

According to some embodiments, the matrix composition of the inventionmay comprise, in addition to the antibiotic agent and/or antifungalagent, another pharmaceutically active agent selected from steroidsand/or non-steroidal anti-inflammatory drugs (NSAID).

Any suitable NSAID may be integrated into the matrix composition forsustained and/or controlled release. Non limiting examples of NSAIDinclude ibuprofen, flurbiprofen, aminosalicylate sodium, cholinemagnesium trisalicylate, choline salicylate, diclofenac, diflunisal,etodolac, fenoprofen, indomethacin, ketoprofen, ketolac tromethamine,magnesium salicylate, meclofenamate, mefenamic acid, nabumetone,naproxen, oxaprozin, oxyphenbutazone, piroxicam, salsalate, sulindac andtolmetin. Each NSAID listed represents a separate embodiment of thepresent invention.

Any suitable steroidal anti-inflammatory drug may be integrated into thematrix composition. Non limiting examples of steroidal anti-inflammatorydrugs (SAIDs) to be used in the formulations of the present inventioninclude, but are not limited to, Corticosteroids such as: betamethasone,betamethasone valerate, cortisone, dexamethasone, dexamethasone21-phosphate, fludrocortisone, flumethasone, fluocinonide, fluocinonidedesonide, fluocinolone, fluocinolone acetonide, fluocortolone,halcinonide, halopredone, hydrocortisone, hydrocortisone 17-valerate,hydrocortisone 17-butyrate, hydrocortisone 21-acetatemethylprednisolone, prednisolone, prednisolone 21-phosphate, prednisone,triamcinolone, triamcinolone acetonide, cortodoxone, fluoracetonide,fludrocortisone, difluorsone diacetate, flurandrenolone acetonide,medrysone, amcinafel, amcinafide, betamethasone and its other esters,chloroprednisone, clorcortelone, descinolone, desonide, dichlorisone,difluprednate, flucloronide, flumethasone, flunisolide, flucortolone,fluoromethalone, fluperolone, fluprednisolone, meprednisone,methylmeprednisolone, paramethasone, cortisone acetate, hydrocortisonecyclopentylpropionate, cortodoxone, flucetonide, fludrocortisoneacetate, flurandrenolone acetonide, medrysone, amcinafal, amcinafide,betamethasone, betamethasone benzoate, chloroprednisone acetate,clocortolone acetate, descinolone acetonide, desoximetasone,dichlorisone acetate, difluprednate, flucloronide, flumethasonepivalate, flunisolide acetate, fluperolone acetate, fluprednisolonevalerate, paramethasone acetate, prednisolamate, prednival,triamcinolone hexacetonide, cortivazol, formocortal and nivazol.

In specific embodiments, the matrix composition is substantially free ofwater. “Substantially free of water” as used herein refers, in oneembodiment, to a composition containing less than 5% water by weight. Inanother embodiment, the term refers to a composition containing lessthan 4.5% water by weight. In another embodiment, the term refers to acomposition containing less than 4.0% water by weight. In anotherembodiment, the term refers to a composition containing less than 3.5%water by weight. In another embodiment, the term refers to a compositioncontaining less than 3.0% water by weight. In another embodiment, theterm refers to a composition containing less than 2.5% water by weight.In another embodiment, the term refers to a composition containing lessthan 2.0% water by weight. In another embodiment, the term refers to acomposition containing less than 1.5% water by weight. In anotherembodiment, the term refers to a composition containing less than 1.0%water by weight. In another embodiment, the term refers to the absenceof amounts of water that affect the water-resistant properties of thecomposition. In another embodiment, the term refers to a compositionmanufactured without the use of any aqueous solvents. In anotherembodiment, producing the composition using a process substantially freeof water, as described herein, enables lipid saturation. Lipidsaturation confers upon the matrix composition ability to resist bulkdegradation in vivo; thus, the matrix composition exhibits the abilityto mediate extended release on a scale of several days, weeks or months.

In another embodiment, the matrix composition is substantially free ofunbound water. In another embodiment, the term refers to a compositionnot containing detectable amounts of unbound water. The term “unboundwater”—refers to free water, which is not part of the thin water film(usually a few molecules thick) formed on the surface of macromolecules(e.g. phospholipids and polymers). The total amount of water in thecomposition may be determined by any method known in the art such asKarl Fischer and loss on drying methods. The ratio between bound andunbound water may be determined for example by differential scanningcalorimeter (DSC).

Technology Platform of the Substrate Impregnated or Coated Fully orPartially with the Matrix Composition Used in Methods of the PresentInvention

According to some embodiments, the coating matrix composition has ahighly organized multilayer structure in which the polymer andassociated cholesterol form one type of layer, the phospholipids form asecond type of layer, and the two types of layers are organized in theform of multiple alternating or quasi-alternating layers.

According to some embodiments, the coating matrix composition of thepresent invention comprises a continuous structure devoid of internalgaps and/or free volume. According to some embodiments, the coatingmatrix composition is lipid-saturated, indicating that the space betweenthe polymer layers or polymer backbone is filled with lipid molecules incombination the pharmaceutically active agent (e.g. an antibiotic agentand/or antifungal agent), to the extent that additional lipid moietiescan no longer be incorporated into the matrix to an appreciable extent.

The coating matrix compositions disclosed herein are lipid saturated.“Lipid saturated,” as used herein, refers to saturation of the polymerof the matrix composition with the first lipid component (e.g.cholesterol) and the second lipid component (e.g. phospholipids) incombination with any pharmaceutical agent present in the matrix, and anyother lipids that may be present. The matrix composition is saturated bywhatever lipids are present. In another embodiment, “lipid saturation”refers to filling of internal gaps (free volume) within the lipid matrixas defined by the external border of the polymeric backbone. The gapsare filled with phosphatidylcholines in combination with cholesterol andpossibly other type of lipids and antibiotic agent present in thematrix, to the extent that additional lipid moieties can no longer beincorporated into the matrix to an appreciable extent. Lipid-saturatedmatrices of the present invention exhibit the additional advantage ofnot requiring a synthetic emulsifier or surfactant such as polyvinylalcohol; thus, matrix compositions of the present invention aretypically substantially free of polyvinyl alcohol.

In some embodiments, the coating matrix composition is capable ofreleasing at least 30% of the active agent at zero-order kinetics whenit is maintained in an aqueous medium (when it is hydrated). In someembodiments, at least 40% of the pharmaceutically active agent isreleased from the matrix composition at zero-order kinetics when it ismaintained in an aqueous medium. In some embodiments, at least 50% ofthe pharmaceutically active agent is released from the matrixcomposition at zero-order kinetics when it is maintained in an aqueousmedium. Without being limited by a specific theory or mechanism ofaction it is suggested that the organized structure or substructure ofthe matrix composition of the invention is one of the main reasons forthe zero-order release rate of the drug or drugs from the matrixformulation following its hydration. Thus, the zero order release ratemay be attributed to slow and continuous “peeling” of the hydratedsurface layer(s) of the highly organized layers of lipids and polymer,with concomitant release of the drug as the components of the surfacelayer are removed from the matrix. It is surmised that this processslowly repeats itself, releasing drug(s) at a steady rate over days,weeks or even months, until the matrix has been completely degraded.Without wishing to be bound by theory, it is believed that the polymerform a first type of layer, and that the phospholipid(s) forms a secondtype of layer, and that these layers alternate i.e.(polymer)-(phospholipid)-(polymer)-(phospholipid); the term“quasi-alternation” is used herein to refer to the situation in whichthere is alternation of more than one instance of a type of layer, e.g.(polymer)-(phospholipid)-(phospholipid)-(polymer)-(phospholipid)-(phospholipid)-(polymer).It is assumed that the cholesterol molecules are located in between thetwo layer, the polar head group pointing towards the polymer and thehydrophobic part between the phospholipid molecules.

In some embodiments, the matrix composition has multiple mixed layers ofpolymer and phospholipid as described supra and it is not in the form ofa microsphere, a micelle, a reversed micelle or a liposome. In someembodiments, the matrix composition does not comprise micelles, reversemicelles or liposomes.

According to some embodiments the matrix of the present invention iswater resistant. As such water cannot easily, if at all, diffuse intothe inner layers of the matrix and the pharmaceutically active agententrapped between the inner layers cannot easily, if at all, diffuse outof the matrix. More particularly it refers to a composition having itsbulk (e.g. part of the composition which is surrounded by an externalsurface, said external surface is exposed to the surroundingenvironment) not exposed to water, or exposed to the extent that theamount of penetrating water is small and insufficient to cause matrixbulk disintegration or degradation. Without wishing to be bound bytheory or mechanism of action, the water resistance properties of thematrix composition, together with its unique multilayered structureconfer the matrix with its sustained release properties, e.g. itsability to release at least 30% of the pharmaceutically active agent(e.g. an antibiotic agent) from the composition at zero order kineticsfor periods of time ranging from several days, weeks and even months,when the composition is maintained in an aqueous environment atphysiological temperature.

The efficacy of a drug is commonly determined by its localconcentration. That, in turn, is determined by the ratio between theaccumulation rate of drug released from the product vs. its eliminationby physical distribution to surrounding tissue, as well as byneutralization and/or degradation. An optimal drug delivery systemshould release the drug according to the biological need, in order tocreate an effective concentration at close proximity to the target andthroughout a sufficient period of time needed for the desired biologicaleffect. This can be achieved by releasing the active form of the drugnear the target at a rate that will result in an effective concentrationthat is above the minimal effective rate, but below the toxic level andfor the desired period of time needed for effective therapeutic effect.

One of the ways to gain better control over local exposure of a givendrug is by controlling its supply rate. The supply rate is dictatedby 1) the drug release profile, 2) the release rate and 3) the durationof release. These parameters are closely related; while the release rateis strongly depended on the specific formulation, the duration is afunction of two factors: release rate and the size of drug reservoir.

The matrix composition of the invention comprising a combination ofspecific lipids and polymers loaded with a drug, preferably anantibiotic agent, determines not only the release rate profile of thedrug, but also allows control over the release rate during a prolongedzero-order kinetic stage. Without wishing to be bound by theory ormechanism of action it is suggested that the most effective profile willcombine initial release, resulting with an effective local concentrationof the drug, followed by continuous, zero order kinetics, release oversufficient duration, for example up to 2 months, up to 7 weeks, up to 6weeks, up to 5 weeks, up to 4 weeks, up to 3 weeks, up to 2 weeks,preferably at least 3-4 weeks. The initial release should be limited soas to leave sufficient reservoir to support subsequent prolong release.

According to some embodiments, when maintained in an aqueous medium atphysiological temperatures, 1 to 50% of said pharmaceutically activeagent is released from the matrix composition by the end of the firstday, 10 to 100% of said pharmaceutically active agent is released fromthe matrix composition by the end of the first week, 20 to 100% of saidpharmaceutically active agent is released from the matrix composition bythe end of the first two weeks and 30 to 100% of said pharmaceuticallyactive agent is released by the end of the first three weeks. In someembodiments, when maintained in an aqueous medium at physiologicaltemperatures, at least 10% but not more than 60% of the pharmaceuticallyactive agent is released by the end of the first week, at least 20%, butnot more than 80% of the pharmaceutically active agent is released bythe end of the second week, at least 30% of the pharmaceutically activeagent is released by the end of the third week. At least 40% of thepharmaceutically active agent is released by the end of the third week.At least 50% of the pharmaceutically active agent is released by the endof the third week. At least 60% of the pharmaceutically active agent isreleased by the end of the third week. According to currently preferredembodiments, the pharmaceutically active agent is an antibiotic agent.

According to some exemplary embodiments, It has been shown (see Examples1 and 2) that substrate particles (e.g. tri-calcium phosphate orpolyvinyl alcohol) impregnated/coated with a matrix compositioncomprising about 15-25% (w/w) of PLGA, about 5-15% (w/w) of cholesterol,about 50-70% (w/w) of a mixture of DPPC and DSPC wherein the ratio ofDPPC and DSPC is between about 5:1 and 2:1 and about 7-12% (w/w) ofdoxycycline, displays initial release of up to about 35% of theentrapped antibiotic and preferably up to 30% of the entrappedantibiotic. The amount of drug released immediately post hydration isclinically safe and leaves most of the drug (at least 65%) to prolongeddelivery for at least 30 days. and can elevate local concentration ofdoxycycline to 10-50 MIC or more. The substrate impregnated or coatedfully or partially with the matrix composition used in methods of thepresent invention gradually releases the pharmaceutically active agent(e.g. antibiotic agent) at a constant release rate (between about 1.5-5%(weight percent of the pharmaceutically agent released per day/totalweight of pharmaceutically active agent initially encapsulated in thematrix composition)), resulting with a local concentration of the drugthat is at least 10 times the (minimal inhibitory concentration (MIC) ofthe antibiotic against pathogens most common is cases of surgical siteinfection (e.g. S. aureus bacteria) over up to 5 weeks.

The substrate impregnated or coated fully or partially with the matrixcomposition used in methods of the present invention enables to entrap alarge variety of one or more biologically active molecules and torelease them at a pre-programmed rate for periods ranging from severaldays to several weeks.

The substrate impregnated or coated fully or partially with the matrixcomposition used in methods of the present invention releases thepharmaceutically active agent locally at a predictable, long-term rate.Thus, the therapeutic drug levels can be maintained locally at thesurgical site (e.g. incision site), while maintaining low or no systemiclevels. Due to the prolonged local release of the pharmaceutical agent,a small and safe dose of local pharmaceutical agent, which, in somecases, be equal to not more than a single dose commonly administeredI.V., is highly effective in eradicating local bacterial infections insurgical sites. By way of example, the amount of antibiotic (e.g.doxycycline) in 5 grams of the substrate impregnated or coated fully orpartially with the matrix composition used in methods of the presentinvention is about the same as the amount of antibiotic in a single dosecommonly administered I.V. or a single pill (or tablet) for oral use.

Additionally, the coating matrix composition acts like a reservoir inwhich the entrapped pharmaceutical agent is protected. In contrast tothe conventional polymer based delivery systems, this characteristic canprotect sensitive drugs reservoir not only from biological degradationagents such as enzymes, but also from chemical destruction due to invivo soluble materials and hydration. When prolong effect is needed,this characteristic is becoming highly important.

“Zero-order release rate” or “zero order release kinetics” means aconstant, linear, continuous, sustained and controlled release rate ofthe pharmaceutical active agent from the polymer matrix, i.e. the plotof amounts of pharmaceutical active agent released vs. time is linear.According to some embodiments, at least 30% of the pharmaceuticallyactive agent is released from the matrix composition at zero orderkinetics at a rate between about 1-7%, 1.5-6%, 1.5-5%, 2-4%, 1.5-3%(weight percent of the pharmaceutically agent released per day/totalweight of pharmaceutically active agent initially encapsulated in thecomposition), each possibility represent a separate embodiment of theinvention.

Lipids

“Phospholipids” are phosphoglycerides having a single phosphatidyllinkage on a glycerol backbone and fatty acids at the remaining twopositions. However, it is to be understood explicitly thatphosphoglycerides having hydrocarbon chains other than fatty acidresidues including alkyl chains, alkenyl chains or any other hydrocarbonchain of at least 12 carbons, alternatively, at least 14 carbons areincluded within the scope of the present invention. The linkage may bean ether linkage instead of an acyl linkage found in phospholipids.

“Phosphatidylcholine” refers to a phosphoglyceride having aphosphorylcholine head group. This phospholipid is composed of a cholinehead group and glycerophosphoric acid, with a variety of fatty acidsmoieties. The fatty acids moieties are typically naturally occurring. Insome embodiments, the fatty acid moieties are saturated. In someembodiments, the fatty acid moieties are unsaturated. “Saturated”,refers to the absence of a double bond in the hydrocarbon chain. Inanother embodiment, the fatty acid moieties have at least 12 carbonatoms. In another embodiment, the fatty acid moieties have 14 carbonatoms. In another embodiment, the fatty acid moieties have 16 carbonatoms. In another embodiment, the fatty acid moieties have 18 carbonatoms. In another embodiment, the fatty acid moieties have 14-18 carbonatoms. In another embodiment, the fatty acid moieties have 14-16 carbonatoms. In another embodiment, the fatty acid moieties have 16-18 carbonatoms. In another embodiment, the fatty acid moieties are chosen suchthat the gel-to-liquid-crystal transition temperature of the resultingmatrix is at least 40° C. In another embodiment, the fatty acid moietiesare both arachidoyl. Each possibility represents a separate embodimentof the present invention.

In another embodiment, the phosphatidylcholine is a naturally-occurringor a synthetic phosphatidylcholine. According to one embodiment, thephosphatidylcholine is a symmetric phosphatidylcholine (i.e. aphosphatidylcholine wherein the two fatty acid moieties are identical(e.g.) dimyristoyl phosphatidylcholine (DMPC),dipalmitoyl-phosphatidylcholine (DPPC),1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC),dioleoyl-phosphatidylcholine (DOPC). In another embodiment, thephosphatidylcholine is an asymmetric phosphatidylcholine (e.g.1-palmitoyl-2-stearoyl-pho sphatidylcholine (PSPC);1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC),1-Stearoyl-2-Arachidonoyl-Phosphatidylcholine (SAPC),2-Arachidonoyl-1-palmitoyl-sn-glycero-3-phosphocholine (APPC)). Inanother embodiment, the phosphatidylcholine is any otherphosphatidylcholine known in the art. Each phosphatidylcholinerepresents a separate embodiment of the present invention.

According to certain embodiments, the at least one phosphatidylcholinein matrix composition suitable for preventing and/or treating surgicalsite infections is selected from the group consisting of DMPC, DPPC,DSPC, DOPC and any combination thereof. Alternatively, the at least onephosphatidylcholine is selected from DMPC, DPPC or a combinationthereof. Alternatively, the at least one phosphatidylcholine is selectedfrom DPPC, DSPC or a combination thereof. Alternatively, the at leastone phosphatidylcholine is selected from DMPC, DPPC or a combinationthereof. Alternatively, the at least one phosphatidylcholine is selectedfrom DMPC, DOPC or a combination thereof.

“Phosphatidylethanolamine” consists of a combination of glycerolesterified with two fatty acids and phosphoric acid. Whereas thephosphate group is combined with ethanolamine. In one embodiments, thefatty acids moieties may be saturated or unsaturated. In anotherembodiment, the fatty acid moieties have at least 14 carbon atoms. Inanother embodiment, the fatty acid moieties have at least 16 carbonatoms. In another embodiment, the fatty acid moieties have 14 carbonatoms. In another embodiment, the fatty acid moieties have 16 carbonatoms. In another embodiment, the fatty acid moieties have 18 carbonatoms. In another embodiment, the fatty acid moieties have 14-18 carbonatoms. In another embodiment, the fatty acid moieties have 14-16 carbonatoms. In another embodiment, the fatty acid moieties have 16-18 carbonatoms. In another embodiment, the fatty acid moieties are chosen suchthat the gel-to-liquid-crystal transition temperature of the resultingmatrix is at least 40° C. The two fatty acids may be the same, ordifferent, and are usually attached to the 1,2 positions of the glycerolmoiety. Non limiting examples of suitable phosphatidylethanolamines aredimethyl dimyristoyl phosphatidylethanolamine (DMPE),dipalmitoyl-phosphatidylethanolamine (DPPE),dilauroylphosphatidylethanolamine (DLPE),distearoylphosphatidylethanolamine (DSPE),dioleoylphosphatidylethanolamine (DOPE),1-palmitoyl-2-oleylphosphatidylethanolamine (POPE),1-oleyl-2-palmitoylphosphatidylethanolamine (OPPE), anddierucoylphosphatidylethanolamine (DEPE). In another embodiment, thephosphatidylethanolamine is any other phosphatidylethanolamine known inthe art. Each phosphatidylethanolamine represents a separate embodimentof the present invention.

“Sterol” in one embodiment refers to a steroid with a hydroxyl group atthe 3-position of the A-ring. According to some embodiments, the sterolconstitutes up to about 40% (w/w) of the weight of the matrixcomposition. In another embodiment, the sterol of methods andcompositions of the present invention is a zoosterol. In anotherembodiment, the sterol is cholesterol.

In another embodiment, a composition of the present invention furthercomprises a lipid other than phosphatidylcholine,phosphatidylethanolamine, or a sterol. In another embodiment, theadditional lipid is a phosphoglyceride. In another embodiment, theadditional lipid is selected from the group consisting of aphosphatidylserine, a phosphatidylglycerol, and a phosphatidylinositol.In another embodiment, the additional lipid is selected from the groupconsisting of a phosphatidylserine, a phosphatidylglycerol, aphosphatidylinositol, and a sphingomyelin. In another embodiment, theadditional lipid is selected from the group consisting of aphosphatidylserine, a phosphatidylglycerol, a phosphatidylinositol, asphingomyelin and a ceramide. In another embodiment, a combination ofany 2 or more of the above additional lipids is present. In anotherembodiment, the polymer, phosphatidylcholine, phosphatidylethanolamine,sterol, and additional lipid(s) are all incorporated into the matrixcomposition. Each possibility represents a separate embodiment of thepresent invention.

Additional Components

In another embodiment, a matrix composition of methods and compositionsof the present invention further comprises a free fatty acid. Nonlimiting examples of free fatty acids that can be incorporated in thecoating matrix composition of the invention are selected from omega-6fatty acid, omega-9 fatty acid, a free fatty acid having 14 or morecarbon atoms, a free fatty acid having 16 or more carbon atoms, a freefatty acid having 16 carbon atoms, a free fatty acid having 18 carbonatoms, a free fatty acid having 16-22 carbon atoms, a free fatty acidhaving 16-20 carbon atoms, a free fatty acid having 16-18 carbon atoms,a free fatty acid having 18-22 carbon atoms, a free fatty acid having18-20 carbon atoms, linoleic acid, linolenic acid and oleic acid. Inanother embodiment, the free fatty acid is another appropriate freefatty acid known in the art. In another embodiment, the free fatty acidadds flexibility to the matrix composition. In another embodiment, thefree fatty acid slows the in vivo release rate. In another embodiment,the free fatty acid improves the consistency of the in vivo controlledrelease. The fatty acid may be unsaturated or saturated. In anotherembodiment, incorporation of a saturated fatty acid having at least 14carbon atoms increases the gel-fluid transition temperature of theresulting matrix composition. Each type of fatty acid represents aseparate embodiment of the present invention.

In another embodiment, a matrix composition of methods and compositionsof the present invention further comprises a tocopherol (e.g. E307(α-tocopherol), β-tocopherol, E308 (γ-tocopherol), E309 (δ-tocopherol).According to some embodiments, the tocopherol may be incorporated intothe matrix instead or in addition to the first lipid having a polargroup (e.g. a sterol, a cholesterol). Each possibility represents aseparate embodiment of the present invention.

In another embodiment, a matrix composition of methods and compositionsof the present invention further comprises physiologically acceptablebuffer salts, which are well known in the art. Non-limiting examples ofphysiologically acceptable buffer salts are phosphate buffers. A typicalexample of a phosphate buffer is 40 parts NaCl, 1 part KCl, 7 partsNa₂HPO₄.2H₂O and 1 part KH₂PO₄. In another embodiment, the buffer saltis any other physiologically acceptable buffer salt known in the art.Each possibility represents a separate embodiment of the presentinvention.

Therapeutic Methods

The methods of the invention directed at preventing and treatingsurgical site infections address medical needs that are currentlylacking effective solutions and that are of great concern to the medicalcommunity. The methods of the present invention provide localizedinfection treatment and prevention to be applied during and/or aftersurgical procedures. The methods of the invention reduce the overallinfection rate and overcome or reduce existing infections, includinghospital-acquired resistant bacteria. The methods of the invention maybe used for treatment and prophylaxis of postoperative infections in avariety of tissues and solid organs.

According to some embodiments the methods for preventing, inhibiting ortreating a surgical site infection in a subject are suitable forsuppressing surgical site infections in general and in particular,surgical site infections associated with orthopedic surgical operations(e.g. hip arthroplasty, knee arthroplasty, total joint replacement,trauma), spine surgical operations, surgical operations on a digestivesystem organ (e.g. esophagus, stomach, small intestine, large intestine,rectum, colon, appendix, liver, pancreas, gallbladder, gastric ulcer,gastric cancer procedures, open gastric bypass, appendectomy, colectomy,cholecystectomy, vagotomy, open billary tract procedures, smallintestine procedures, colorectal procedures), cardiac procedures (e.g.coronary artery bypass, cardiothoracic transplantation procedures,cardiac device insertion procedures), hernia repair, vascularprocedures, caesarian, prostatectomy, obstetric and gynecologic surgicaloperations (e.g. hysterectomy), head and neck cancer surgery,transplantation surgeries (e.g. lung, liver, pancreas, kidney),neurosurgery (e.g. deep brain stimulation implant) and plastic surgeries(e.g. breast reconstruction, mastectomy).

According to specific embodiments, the present invention providesmethods for preventing, inhibiting or treating sternal wound siteinfection associated with cardiac surgery procedures comprising the stepof applying to the sternal halves surface and/or surrounding soft tissuea biodegradable substrate being impregnated and/or having its surfacecoated fully or partially with a matrix composition comprising (a) abiocompatible polymer, (b) a first lipid component comprising a sterol,(c) a second lipid component comprising at least one phospholipid havingfatty acid moieties of at least 12 carbons; and (d) a pharmaceuticallyactive agent selected from the group consisting of an antibiotic agent,antiseptic agent, an anti-inflammatory agent, anti-fungal agent and anycombination thereof. According to some embodiments, the pharmaceuticallyactive agent is an antibiotic agent. According to some embodiments, theantibiotic agent is doxycycline or doxycycline hyclate. The methods forpreventing, inhibiting or treating sternal wound infection associatedwith cardiac surgery further encompass the prevention or suppression ofsternal wound biofilm formation following cardiac surgery. As usedherein, “sternal wound site infection” encompasses both superficial anddeep sternal wound complications.

According to specific embodiments, the present invention providesmethods for preventing, inhibiting or treating sternal wound siteinfection associated with cardiac surgery procedures comprising the stepof applying to the sternal halves surface and/or surrounding softtissue, tri-calcium phosphate particles or polyvinyl alcohol particlesimpregnated/coated with a matrix composition comprising about 15-25%(w/w) of PLGA, about 5-15% (w/w) of cholesterol, about 50-70% (w/w) of amixture of DPPC and DSPC wherein the ratio of DPPC and DSPC is betweenabout 5:1 and 2:1 and about 7-12% (w/w) of doxycycline.

According to some embodiments, the substrate impregnated or coated fullyor partially with the composition according to the methods of theinvention, may be administered to the surgical site (e.g. incision site)directly to or proximal to the site of incision. In some embodiments,the impregnated/coated substrate may be administered to the surgicalsite (e.g. incision site) by sprinkling the impregnated/coated substrateparticles onto a surgical site and its vicinity. According to someembodiments the coated substrate is formulated as a powder. According tosome embodiments, coated substrate particles may be sprinkled over thesurgical site and its vicinity using a salt shaker-like container ordispenser. A salt shaker-like container or dispenser as used hereinrefers to a container defining a cavity (e.g. a tubular cavity) forstoring the coated substrate powder, and which has at least one aperturethrough which the coated substrate particles may be dispensed. Inanother embodiment, the substrate impregnated or coated fully orpartially with the composition according to some embodiments of theinvention, may be injected to the surgical site (e.g. incision site) andits surroundings. Alternatively, substrates in the form of a sponge, afoam or a sheet impregnated or coated fully or partially with thecomposition according to some embodiments of the invention, may beadministered to the surgical site by placing them over the surgical siteor its surrounding, for example by covering the surgical site with atleast one piece of a gelatin or collagen sponge, foam or sheetimpregnated or coated with the matrix composition. Alternatively, thebiocompatible substrates impregnated or coated fully or partially withthe composition according to some embodiments of the invention, may beformulated as a paste and spread over the surgical site and itsvicinity. Typically, a paste like structure is obtained by hydrating adrug coated substrate disclosed herein with an aqueous solution prior toits application. According to some embodiments, hydration shall beperformed not more than 2 hours prior to the application of theresulting paste to the surgical site, preferably up to 1 hour prior tothe application of the resulting paste to the surgical site, morepreferably, not more than 30 minutes prior to its application to thesurgical site. According to some embodiments, a paste texture will beattained when the amount of aqueous solution (for example: saline) mixedwith the drug coated substrates is between 0.1:1 and 1:1 (w/w)respectively; preferably between 0.3:1 and 0.6:1 (w/w) respectively.

The present invention provides methods for preventing or treating asurgical site infection associated with a surgical operation comprisingthe step of applying to the surgical site a biodegradable substratebeing impregnated and/or having its surface coated fully or partiallywith a matrix composition which provides local controlled and prolongedrelease of at least one pharmaceutically active agent at the surgicalsite. In some embodiment the matrix composition incorporates a pluralityof pharmaceutically active agents. According to some embodiments, thesubstrate coated with the matrix composition of the present inventionmay be administered substantially as a single ingredient (notadministered as part of a mixture with other ingredients).Alternatively, it may be applied to the surgical site as a combinationof two or more populations of differently coated substrates. Forexample, the methods may comprise the step of applying to the surgicalsite a combination of a first population of coated substrates comprisingone antibiotic agent mixed with a second population of coated substratescomprising a different antibiotic agent.

As described above, the amounts, ratios and types of ingredients formingthe matrix composition of the present invention may be varied so toadjust the polymer-lipid basis to the biophysical/biochemical propertiesof the drug, the therapeutically effective dose of the drug and to thedesired release rate and/or the duration of release of the drug. Themethods of the invention therefore encompass the step of application tothe surgical site of a combination of two or more populations of coatedsubstrates, each capable of releasing the drug at a different rateand/or duration, the drug in the different coated substrate populationsmay be the same or different. Without wishing to be bound by theory ormechanism of action, application to the surgical site of a combinationof coated substrate populations, each comprising a different drugformulated to be released at a predetermined rate and/or duration,provides the clinician or skilled artisan with great flexibility inadjusting the treatment protocol according to the medical need. Anon-limiting example may be a combination of two populations of drugcoated substrates, one comprising a first antibiotic agent released forabout 3-4 weeks and a second population of drug coated substratescomprising a second antibiotic agent released for about 1-2 weeks.

It is to be emphasized that the substrates coated/impregnated with amatrix composition according to embodiments of the invention, may beprovided to the clinician or skilled artisan as a pre-mixed combinationof two or more populations of coated substrate or preferably, as singleingredients (not part of a mixture with other ingredients) to be mixedby the skilled artisan prior to application to the surgical site.

Methods of Making Matrix Compositions

In order to obtain the compositions of the invention any suitable methodmay be employed that will yield a homogeneous dispersion of the polymerand the lipids in a water resistant matrix. Advantageously according tosome embodiments the methods employed eschew the use of water at anystage of the manufacturing process.

Advantageously, the matrix compositions of the present invention areprepared by methods which do not involve the formation of emulsions, andmay avoid the use of aqueous media altogether. The generation ofemulsions that are subsequently dried necessarily results in vesicles ormicrospheres. In order to produce coated articles the mixture ofpolymer, lipids and antibiotics within the appropriate selected volatileorganic solvents will be used to coat the desired surface.

According to some embodiments the polymer and sterol are mixed withappropriate selected volatile organic solvent(s) on the one hand and thephospholipids together with the active pharmaceutical agent are mixedwith its appropriate selected solvent(s) or solvents prior to mixingtogether with the polymer/sterol mixture.

In certain embodiments, the present invention provides a method ofproducing a matrix composition, the method comprising the steps of:

(a) mixing into a first volatile organic solvent: (i) a biodegradablepolyester and (ii) sterol; and

(b) mixing separately into a second volatile organic solvent: (i) anactive agent; (ii) a phosphatidylcholine or a mixture ofphosphatidylcholines and optionally (iii) an additional lipid componentsuch as, for example, a phosphatidylethanolamine;

(c) mixing and homogenizing the products resulting from steps (a) and(b); and

(d) bringing the substrate into contact with the homogenous mixtureresulting from step (c).

In another embodiment, phosphatidylethanolamine may be included in thevolatile organic solvent of step (a) instead of or in addition to aphosphatidylethanolamine added to the volatile organic solvent of step(b). In another embodiment, the biodegradable polyester is selected fromthe group consisting of PLA, PGA and PLGA. In another embodiment, thebiodegradable polyester is any other suitable biodegradable polyesterknown in the art. In some embodiments the first volatile organic solventis a non-polar solvent. In some embodiments the second volatile organicsolvent is a water miscible solvent. In cases where the active agent isa protein or peptide it is important to select solvents that will notdenature or impair the activity of the protein.

In another embodiment, the mixture of step (a) containing a volatileorganic solvent is homogenized prior to mixing it with the solution ofstep (b). In another embodiment, the volatile organic solvent or mixtureof volatile organic solvents used in step (a) may be same or differentthan the volatile organic solvent or mixture of organic solvents used instep (b). In another embodiment, the mixture of step (b) is homogenizedprior to mixing it with the mixture of step (a). In another embodiment,the polymer in the mixture of step (a) is lipid saturated. In anotherembodiment, the matrix composition is lipid saturated. Preferably, thepolymer and the phosphatidylcholine are incorporated into the matrixcomposition. In another embodiment, the active agent as well isincorporated into the matrix composition

In another embodiment, each step of the production method issubstantially free of aqueous solution. In another embodiment, each stepis substantially free of the presence of water or any aqueous solution.

Upon mixing, a homogenous mixture is formed. The substrate to be coatedor impregnated with the matrix composition is combined with saidhomogenous mixture.

The production method further comprises the step of evaporating thesolvent present in the product of step (d). Solvent evaporation istypically done by heating the product of step (d). The heating iscontinuing until the solvent is eliminated and in a typical temperaturebetween room temperature to 60° C., preferably at a temperature below50° C., more preferably at a temperature of 45° C. or lower, morepreferably at a temperature of 30° C. or lower. According to someembodiments, mild vacuum (e.g. 300-600 psi) is applied during thesolvent evaporation step. In another embodiment a step of vacuum-dryingis performed following the step of solvent evaporation. Each possibilityrepresents a separate embodiment of the present invention.

Methods for the determination of lipid saturation: The following methodmay be used to determine the degree of lipid saturation:

(i) Following manufacture, the matrix composition is hydrated andisolated by centrifugation or filtration. Lipids that not entrapped inthe matrix form free micelles or liposomes and are located in thesupernatant. The overall lipid contents of the supernatant and thematrix are quantified. In this manner, the entrapped vs. free lipidcontents are determined for various formulation containing differentlipid:polymer ratios at the outset. Thus, the actual, experimental,maximum lipid/polymer ratio is determined.

(ii) Following manufacture, the matrix composition is hydrated with asolution containing tritium-tagged water, washed with tritium-freesolution, and isolated by centrifugation or filtration, and the amountof water entrapped per polymer mass is quantified. This is repeated withdifferent lipid:polymer ratios, in order to determine the amount oflipids required to saturate the free volume in the matrix composition.

EXPERIMENTAL DETAILS SECTION

Abbreviations used: phosphoethanolamine=PE; phosphatidylcholine=PC;1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine=DMPE (14:0);1,2-dipalmito yl-sn-glycero-3-phosphoethanolamine=DPPE (16:0);1,2-distearoyl-sn-glycero-3-phosphocholine=DSPC (18:0);1,2-dipalmitoyl-sn-glycero-3-phosphocholine=DPPC (16:0); Tri-calciumphosphate (TCP); poly vinyl alcohol (PVA).

Example 1: Process for the Preparation of a Substrate (e.g. Tri-CalciumPhosphate Particles, Poly Vinyl Alcohol Particles) Coated/Impregnatedwith a Doxycycline Containing Matrix Composition According to CertainEmbodiments of the Invention (for the Treatment and Prevention ofSurgical Site Infections)

Overview: To produce lipid-saturated polymer matrices, two mixtures arecreated.

1. A biodegradable polymer and a first lipid component (e.g. sterol) aremixed with a volatile organic solvent, which is mixed to yield asolution or suspension of lipid-saturated polymer matrix, as measured byits differential scanning calorimetric (DSC) profile.

2. The active agent and a second lipid component (e.g. at least onephospholipid) are mixed with a second volatile organic solvent to yielda second solution or suspension.

3. The two solutions or suspensions are combined and mixed untilequilibrium is reached.

4. A substrate (e.g. gelatin sponge, collagen foam, mineral substrate)is then mixed with the resulting solution of stage 3.

5. The organic solvents are then evaporated, yielding a substrate coatedand/or impregnated with a drug-containing, lipid-saturated polymermatrix.

Exemplary Protocol

Tri-calcium phosphate particles having an average diameter of 100 μmwere coated with a matrix composition suitable for sustained release ofdoxycycline by the following process:

1. Preparation of stock solutions:

1.1. Stock solution of PLGA 75/25 (300 mg/ml in ethyl acetate)—PLGA75/25 was weighed into volumetric flask. Ethyl acetate was added tovolume. The solution was stirred until all PLGA grains were completelydissolved.

1.2. Stock solution of Cholesterol (30 mg/ml in ethylacetate)—Cholesterol was weighed into volumetric flask. Ethyl acetatewas added to volume. The solution was vortexed until the cholesterol wascompletely dissolved.

1.3. Stock solution of Doxycycline (210 mg/ml in methanol)—Doxycyclinewas weighed into volumetric flask. Methanol was added to volume. Thesolution was vortexed until the doxycycline was completely dissolved.

1.4. Stock solution of DPPC (206 mg/ml and DSPC 69 mg/ml inmethanol/ethyl acetate mixture (9/14))—DPPC and DSPC were weighed intovolumetric flask. Methanol/ethyl acetate (9/14) was added to volume. Thesolution was incubated at 45° C. for 5 min and vortexed until thephospholipids were completely dissolved.

2. Preparation of the coating solution

Solution A—5 volumes of the cholesterol stock solution were mixed with 1volume of the PLGA stock solution. The mixture contained 50 mg/ml PLGAand 25 mg/ml cholesterol.

Solution B—18 volumes of doxycycline solution were successfully mixedwith 82 volumes of phospholipids solution (see section 1.4.). Themixture contained 225 mg/ml phospholipids (56 mg/ml DSPC and 169 mg/mlDPPC) and 37.5 mg/ml doxycycline.

Solution AB—2 volume of solution B were mixed with 3 volumes of solutionA resulting solution containing 30 mg/ml PLGA 75/25, 15 mg/mlcholesterol, 90 mg/ml phospholipids and 15 mg/ml doxycycline.

3. Substrate coating

1.5 gr. of substrate (e.g. tri-calcium phosphate powder (100 μmparticles), poly vinyl alcohol (PVA) powder, Poly lactic acid (PLA)powder) were weighed into 30 mm glass petri dish.

1.5 ml of solution AB was added to the dish.

The petri dish was placed in a vacuum oven set to 45° C. and partialvacuum was applied ((˜610 mm/Hg) until all solvents evaporated (thepresence of solvents could not be detected) the oven was turned off andfull vacuum was applied to remove any residual solvents (overnight).

The dried coated tri-calcium phosphate powder was transferred into lightprotected vial and stored at 4° C.

Drug release profile: the coated substrate was hydrated (5% serum at 37°C.) and the release of doxycycline from the tri-calcium phosphateparticles impregnated/coated with the matrix composition was followedand quantified by HPLC. The release profile is presented in FIG. 1.

Example 2—Drug Release from PVA Particles Impregnated/Coated with theSustained Release Formulation of the Invention

Coated/impregnated PVA particles were prepared as described above inExample 1. Following hydration (5% serum at 37° C.) the release ofdoxycycline from the PVA particles impregnated/coated with the matrixcomposition was detected and quantified by HPLC. The release profile ispresented in FIG. 2.

As can be seen in FIG. 2, the first hour release reached about 45% ofthe doxycycline in the coating matrix. Further investigation the firsthour release revealed that when the collected sample was centrifuged(spin-down) and further sieved (45 um filter) or vice versa (sieved andfurther centrifuged), the amount of the doxycycline released within thefirst hour and detected by HPLC was lower by at least 50% (e.g. ˜20%).Without being bound by theory or mechanism of action, it is estimatedthat the collected sample (before centrifuging and/or filtering thecollected sample) includes apart from doxycycline molecules that wererelease from the formulation, also small fragments of coated PVAparticles.

Coated and uncoated PVA particles were further analyzed by FTIR and SEM.

No indications to interaction between the PVA particles and the coatingmatrix were found by FTIR.

SEM images of uncoated PVA particles disclose globular particles havinga porous rough terrain surface (FIGS. 3A and 3B). Images of coated PVAshow that both outer and inner surfaces of the particles are coated(FIGS. 3C and 3D).

Without wishing to be bound by theory or mechanism of action, the use ofPVA may be advantageous due to the fact that it is dissolved soon afterthe coating matrix comprising the drug is disintegrated. Exposure of thePVA to body fluids will initiate its degradation and removal, leaving notraces at the treated surgical site.

Example 3—Drug Release from Absorbable Gelatin Sponge Containing theSustained Release Formulation of the Invention

A 1 cm*1 cm piece of collagen sponge was placed in a 20 ml vial. 0.4 mlof solution AB (as described above in Example 1) were added to the vialand the vial was left closed at room temperature for 10 min. The pieceof collagen sponge impregnated with solution AB was transferred to a 4ml vial for evaporation of the solvents followed by vacuum overnight.This collagen piece was put to release experiment.

Following hydration (5% serum at 37° C.) the release of doxycycline fromthe gelatin sponge piece impregnated with the matrix composition intothe surrounding was detected and quantified by HPLC.

Example 4—Pre-Clinical Testing of TCP Granules Coated/Impregnated with aMatrix Composition According to Embodiments of the Present Invention forthe Treatment of Intramuscular Surgical Site Infection

The objective of this study is to assess the efficacy of tri-calciumphosphate granules (˜100 μm) coated with a matrix composition comprisingdoxycycline according to some embodiments of the invention (“Testarticle”) in reducing bacterial proliferation following induction of asurgical site infection (SSI) model attained by intramuscularimplantation of the Test article combined with Staphylococcus aureus(ATCC 25923) in SD rats. The preparation of the “test article” isdescribed in Example 1.

All preclinical testing is performed in accordance with the guidelinesfor Regulation of Animal Experiments in the State of Israel andaccording to the Ethics Committee of the research institution.

Animal model: Sprague Dawley®™ SD®™ male rats, 11-12 weeks of age.

Bacterial Inoculum: Staphylococcus aureus from ATCC 25923 source,provided in a ready to use state divided to two respectiveconcentrations of 1×10⁷ and 1×10⁸ CFU/ml.

Test material: Synthetic tri-calcium phosphate (TCP)—50-100 μmCamBioceramic granules coated with a matrix composition comprisingdoxycycline as described in Example 1, provided as a “ready to use”powder. Prior to surgical procedure, Vehicle Material is asepticallydivided into aliquots of 50±2 mg placed in glass vials (one aliquot perimplantation site).

Constitution of Tests Groups & Doses:

Table 1 below lists the experimental groups comprised in the study:

TABLE 1 Bacterial Inoculum S. aureus S. aureus (ATCC (ATCC Proposed25923) 25923) Treatment Observation Suspension Implanted ImplantedPeriod Group No. of Concentration Volume Implanted Volume Route of (dayspost No. Animals (CFU/ml) (μl) Material (mg) Implantation implantation)1 n = 2 Untreated 14 2 n = 6 1 × 10⁷ 50 TCP 50 Implantation 3 n = 6test- into an article intramuscular 4 n = 6 1 × 10⁸ 50 TCP 50 pocketformed 5 n = 6 test- in the right article gluteal muscle

Test Procedures:

Pre-Surgery Preparations: Animals are administered an opioid analgesic(Buprenorphine at a dose level of ˜0.075 mg/kg) by subcutaneousinjection approximately 1-2 hours prior to surgical procedure. In allcases, animals are subjected to general anesthesia by Isofluraninhalation (2-4% in oxygen at a flow of 0.8-1.2 L/min.).

Implantation of Test Materials into an intramuscular pocket is performedin each animal (excluding untreated animals) under aseptic conditions asfollows:

Animal is placed on a heated surface in prone position. A longitudinalskin incision is performed at the dorsal lumbar area, approximately 2 cmright to the vertebral column and extended until visualization of thegluteal muscles is obtained. A pocket measures approximately 2 cm inlength and 1 cm in depth is formed in the gluteal muscles using bluntdissection technique or a surgical blade.

The Test Material is poured into the pocket directly from the weighingpaper while retracting the pocket's edges with forceps. Subsequently andwhile the pocket's edges are still retracted, 50 μl of the bacterialsuspension (at the respective concentration) or physiological saline (incontrol sample) is administered into the formed pocket using pipette.The musculature and skin are closed by simple interrupted sutures usingappropriate suture materials and surgical clips, respectively.

The closed incision is cleaned of blood residuals by rinsing it withphysiological saline then applied with Polydine solution.

Post-Operative Care: Animals are administered subcutaneously withbuprenorphine at a dose of ˜0.075 mg/kg twice daily for up to 3 dayspost-surgery.

Observations and Examinations: Duration—˜14 days. Clinical signs andbody weight are monitored. Incision sites are inspected and evaluatedonce daily. Additionally, in order to assess a local reaction in deepertissues, sites of surgery are subjected to manual palpation and gradedaccording to a 5-grade scale as follows: 0=no palpable nodule, 1=barelypalpable nodule, 2=nodule 0.25-0.5 cm in diameter, 3-nodule >0.5 cm indiameter, 4=abscess expressed.

The entire implantation site area of all animals, is harvested, weightedand individually placed in a labeled vial filled with 10 ml ofphysiological saline. Vials are placed on ice until performance ofmicrobiological assay.

Quantitation of Bacteria in Tissue:

Each test site is aseptically cut into small pieces using sterilescissors, thus exposing the contents of the pocket.

Suspension of minced tissue in saline is vortexed for 1 min.

10-fold dilutions of suspension in saline are prepared (up to 10-5 forthe highest inoculum size).

Specimens are then plated on selective agar and on blood agar. Followingincubation at 37° C. for 24-48 hours, the number of bacteria recoveredis quantified in each medium and expressed as colony forming units persample.

The efficacy assessment results are presented in the following Table 2and summarized in FIG. 4.

TABLE 2 Treatment S. aureus (ATCC 25923) Quantification of SuspensionBacteria in Samples Animal Implanted Concentration Route of CFU/gr. No.Material (CFU/ml) Implantation CFU/sample of sample 1 UNTREATED 150 44 2150 38 1 TCP NOT Implantation 650 89 2 (Group 1) INDUCED into an 1500313 (sham) intramuscular 3 TCP 1 × 10⁷ pocket formed 316000 43288 4(Group 2) in the right 310000000 62000000 5 gluteal muscle 28000000042424242 6 1830000000 338888889 8 660000000 146666667 9 test article 1 ×10⁷ 800000 150943 10 (Group 3) 79000 17174 12 1150000 396552 13 1300000265306 14 142000 33023 15 TCP 1 × 10⁸ 8950000 2355263 16 (Group 4)243000 65676 17 24500 3356 20 2470000000 475000000 21 test article 1 ×10⁸ 77000 17907 22 (Group 5) 182000 49189 24 2000000 263158 25 355008452 26 306000 62449

Conclusion: The results obtained in this study, including macroscopicobservations, microbiological assay and histopathological evaluation,clearly indicate that a substrate (e.g. Synthetic tri-calcium phosphate)coated with formulation containing doxycycline has significantly reducedbacterial proliferation in an intramuscular surgical site infection(SSI) model in SD rats.

Histopathology—14 days post-surgical procedure, animals were sacrificedand the entire implantation site area was macroscopically evaluated forthe degree of inflammatory reaction. Animals #7, 11, 18 & 23 of groups#. 2, 3, 4 & 5, respectively, were then harvested, weighed and sent formicrobiological evaluation towards quantification of the bacteria in thesamples.

Slides Preparation: histological processing performed as follows: Eachsample was decalcified, trimmed, embedded in paraffin and 3 sections,each approximately at 5 micron thickness, interspaced at about 500micron from each other were performed. Each of the 3 slides was stainedwith Hematoxylin & Eosin (H&E).

Histopathological Evaluation: The amount of residual implanted materialand presence of bacterial colonies were evaluated and scored accordingto the following grading scale: 0=No residual implant/bacterialcolonoies observed, 1=One or two small foci of material/bacterialcolonies, 2=Multiple small, with or without a large focus of residualmaterial/bacterial colonies, 3=Multiple large foci of residualmaterial/bacterial colonies, 4=Abundant residual material/bacterialcolonies filling the surgical site.

RESULTS: Macroscopic Evaluation of Test Sites at Necropsy:

In general, in almost all animals assigned to both TCP treated groups(i.e. groups no. 2 & 4), a bulge measures 0.5-2 cm in diameter wasobserved at the center of the Test Site. Additionally, in few of theTest Sites of groups 2 & 4, adhesion of the skin to the inner tissue wasnoted.

In contrast, only a low rise of in the tissue was detected in the TestSites of 2 out of 6 and 1 out of 6 animals assigned to groups no. 3 & 5,respectively.

Histopathological Findings:

Animal #7 and #18 of Groups 2 and 4 respectively—TCP combined with 1×10⁷or 1×10⁸ CFU/ml of Bacteria: The intramuscular pocket in the glutealmuscle contained collections of polymorphonuclear cell (abscessformation), necrosis and Vehicle Item (TCP) granules surrounded bygranulomatous (i.e., macrophages, giant cells) reaction. The entirereactive site is surrounded by early maturing capsular reaction.Numerous bacterial colonies are also identified, closely and within theabscesses. The abscess formation is scored grade 3.

Animal #11 and #23 of Groups 3 and 5 respectively—“test article”combined with 1×10⁷ or 1×10⁸ CFU/ml of Bacteria: The intramuscularpocket in the gluteal muscle contained collections of Tri CalciumPhosphate (TCP) granules (which is one of the components of theimplanted Test Device) surrounded by granulomatous (i.e., macrophages,giant cells) reaction, and sporadic minimal (grade 1) mononuclear cellinfiltration, indicative of excellent potential in reducing bacterialproliferation.

Conclusion: Samples of groups 2 and 4 (implantation of TCP only): Theintramuscular pocket in the gluteal muscle contained abscess formation,associated with Vehicle Item (TCP) granules and presence of numerousbacterial species. There are no apparent differences in any of thecomponents and/or scores when comparing the reactions seen in samplesfrom groups 2 and 4.

Samples of groups 3 and 5 (“test article”): The intramuscular pocket inthe gluteal muscle contained collections of Tri Calcium Phosphate (TCP)granules surrounded by granulomatous (i.e., macrophages, giant cells)reaction, and sporadic minimal mononuclear cell infiltration, indicativeof excellent potential in reducing bacterial proliferation. There are noapparent differences in any of the components and/or scores whencomparing the reactions seen in samples from groups 3 and 5. It can beconcluded that the test compound was highly effective in reducingproliferation of bacteria at the surgical site.

Example 5—Eradication of an Established Biofilm in the Presence of TCPParticles Coated with a Matrix Composition According to Some Embodimentsof the Invention

The effectiveness of tri-calcium phosphate granules coated with a matrixcomposition according to embodiments of the invention in eradicatingestablished biofilm was measured using the MBEC™ (Minimum BiofilmEradication Concentration) Physiology and Genetics Assay.

MBEC™ Test Method Overview: MBEC™ test method specifies the operationalparameters required to grow and treat different bacterial biofilms in ahigh throughput screening assay. The assay device consists of a plasticlid with ninety-six (96) pegs and a corresponding receiver plate withninety-six (96) individual wells that have a maximum 200 μL workingvolume. Biofilm is established on the pegs in a batch culture basedmodel (i.e., no flow of nutrients into or out of an individual well)with gentle mixing. The established biofilm is transferred to a newreceiver plate for disinfectant efficacy testing.

Sample Description:

Each sample set tested included the following groups listed in the table3 below:

TABLE 3 CODE SAMPLE DESCRIPTION Contact time Concentrations A β-TCPβ-Tri Calcium Phosphate (β-TCP) 24 ± 2 hrs 0.3%, 1%, 3%, 10% & 30% w/v(mg/μl) so in 200 μL, there is 0.6, 2, 6, 20 and 60 mg of the sample,respectively B Test-article Test article formulation: β-TCP 24 ± 2 hrs0.3%, 1%, 3%, 10% & 30% w/v granules coated/impregnated with a (mg/μl)so in 200 μL, there is matrix composition comprising 0.6, 2, 6, 20 and60 mg of the doxycycline hyclate sample, respectively C β-TCP +Doxycycline hyclate non-formulated 24 ± 2 hrs 0.3%, 1%, 3%, 10% & 30%w/v Doxycycline β-Tri Calcium Phosphate (β-TCP) (mg/μl) so in 200 μL,there is and free (not formulated) doxycycline 0.006 at 3%, 0.06 at 3%,0.6, hyclate (10 mg/ml and 5 mg/ml 2, 6, 20 and 60 mg of TCP, solutionsin distilled water). respectively that should be impregnated with 6.72,22.4, 67.2, 224 and 672 μg of the doxycycline, respectively

Test Organisms: Staphylococcus aureus (an osteomyelitis-relatedstrains); source: ATCC 29213; Dilution/Challenge Media: 1,000×TSB+10%human serum 24 hrs; Growth Media/agar: Tryptic Soy Broth/Tryptic Soyagar for 24 hrs Aerobic cond.

TEST METHOD overview: The experimental process for high-throughputantimicrobial susceptibility testing using the hydroxyapatite coatedMBEC™ P&G assay. This standard protocol was broken into a series ofsmall steps, each of which is detailed in the sections below.

1. Culture/Inoculum Preparation:

Using a cryogenic stock (at −70° C.), a first sub-culture ofStaphylococcus aureus was streaked out on OSA (organism specific agar).The plates were incubated at appropriate growth conditions for 20±2.0hours and further stored at 4° C.

A second sub-culture taken from the first sub-culture was streaked outon OSA. The plates were incubated at appropriate growth conditions for20±2.0 hours. An isolated colony from the second sub-culture wasaseptically removed from the OSA plate and inoculated into 50 mL ofsterile bacterial liquid growth broth, followed by incubationappropriate growth conditions for 20±2.0 hours (at 150 rpm).

The inoculum was adjusted to an approximate cell density of 10⁶ CFU/mL.

Samples (100 μL) of the diluted organism were used for an inoculum checkby serially diluting and spot plating on OSA in triplicate.

Preparation of the Challenge Plate:

150 μL of the remaining diluted organism were placed in each of thecorresponding wells of an MBEC™ P&G device except the sterility controls(Table 5). The device was placed on an orbital shaker (110 RPM) in ahumidified incubator at 37±1° C.

Sample Sterility Controls:

Pegs were broken from BGCH wells with flamed pliers. Each peg was placedinto 200 μL of the neutralizer. The pegs were sonicated for 30 minutes.The recovery suspension was then serially diluted and spot plated onOSA. This served as a biofilm growth check.

200 μL of sterile TSB was added to wells GC and SC-M of the challengeplate, respectively. These served as sterility control (SC) and growthcontrol (GC) for each trial of each organism. BGCh is the biofilm GrowthCheck. N wells are the neutraliser toxicity controls and N:50 wells arethe neutraliser efficacy controls.

TABLE 4 Challenge plate β-TCP + Free β-TCP Test-article DoxycyclineGentamicin A A A A B B B C C C 32 32 32  30%  30%  30%  30%  30%  30% 30%  30%  30% B A A A B B B C C C 16 16 16  10%  10%  10%  10%  10% 10%  10%  10%  10% C A A A B B B C C C 8.0 8.0 8.0 3.0% 3.0% 3.0% 3.0%3.0% 3.0% 3.0% 3.0% 3.0% D A A A B B B C C C 4.0 4.0 4.0 1.0% 1.0% 1.0%1.0% 1.0% 1.0% 1.0% 1.0% 1.0% E A A A B B B C C C 2.0 2.0 2.0 0.3% 0.3%0.3% 0.3% 0.3% 0.3% 0.3% 0.3% 0.3% F SC-A SC-A SC-A SC-B SC-B SC-B A A A1.0 1.0 1.0 0.3% 0.3% 0.3% (0.06 (0.06 (0.06 μg μg μg Dox) Dox) Dox) GN:50 N:50 N:50 N N N SC-C SC-C SC-C A A A 0.3% 0.3% 0.3% (0.006 (0.006(0.006 μg μg μg Dox) Dox) Dox) H BGCh BGCh BGCh SC SC SC GC GC GC GC GCGC

Using a sterile 96-well microtitre plate the following was doneaseptically to set up the challenge plates listed in Table 4:

Neutralization control: 200 μL of the neutralizer were added to 300 μgof the doxycycline in the N:50 wells (final concentration of Doxycyclinein D/E (neutralizer) is 1.5 mg/mL).

Neutralizer toxicity control: 200 μL of the neutralizer was added to Nwells.

Biocide sterility control: 60 mg of β-TCP, test article andβ-TCP+Doxycycline were added to SC A-C wells.

Antimicrobial Challenge for Preformed Biofilm:

The biofilm formed on the lid of the MBEC device was rinsed by dippingthe lid into saline (˜30 seconds) to remove planktonic cells. The lidwas then put on top of the challenge plate and incubated on a rotaryshaker at 110 rpm at 35±2° C. for 24±2 hours.

Biofilm Recovery:

After incubation (specified above), planktonic cells were rinsed off thebiofilm by dipping the lid into saline (˜20-30 seconds). The lid wasthen transferred to a neutralizer/recovery plate and put in a sonicator(˜30 minutes) to dislodge surviving biofilm.

Determination of Planktonic MBC:

20 μL from each well of the challenge plate were removed, and placedinto the corresponding wells of a fresh 96 well plate containing 180 μLDE neutralizer. The plate was incubated at 35±2° C. for 24±2 hours. MBCresults were visually determined post incubation.

LOG₁₀ Reduction:

Following sonication, 100 μL from each well of the MBEC™ plate, were putinto the first 12 empty wells of the first row of a 96 well-micro titerplate and were further diluted by 10 fold down each of the 8 rows(10°-10⁷ dilution). 5 μL from each well were then used for spottingprepared OSA plates. The agar plates were incubated at 37±1° C. andcounted after approximately 24-48 hours of incubation. The arithmeticmean of the number of colonies counted on the plates was calculated.

100 μL of the sterile neutralizer was added to each well of the recoveryplate to top up the volume back to 200 μL. The refilled plate isincubated at 35±2° C. for 24±2 hours.

Comparator MBEC results were determined following the 24±2 hourincubation using the plate reader.

The log density for one peg was calculated as follows:

LOG₁₀ (CFU/peg)=LOG₁₀[(X/B) (D)] where: X=mean CFU; B=volume plated(0.02 mL) and D=dilution.

The overall biofilm accumulation was determined by calculating the meanof the log densities calculated.

LOG₁₀ reduction for each dilution was calculated as follows: LOG₁₀Reduction=Mean LOG₁₀ Growth Control—Mean LOG₁₀ Test Sample.

Results:

Average LOG₁₀ CFU/peg recoveries are presented in Table 5:

TABLE 5 Average Log10 CFU/peg recoveries 1 2 3 Average St. Dev A 30.0%3.90 3.60 3.60 3.70 0.17 10.0% 3.60 3.90 3.60 3.70 0.17 3.0% 3.60 3.783.60 3.66 0.10 1.0% 3.60 3.60 3.90 3.70 0.17 0.3% 3.90 3.90 3.60 3.800.17 B 30.0% 0.00 0.00 0.00 0.00 0.00 10.0% 0.00 0.00 0.00 0.00 0.003.0% 0.00 0.00 0.00 0.00 0.00 1.0% 1.91 2.45 0.00 1.45 1.29 0.3% 2.083.30 3.08 2.82 0.65 C 30.0% 0.00 0.00 0.00 0.00 0.00 10.0% 0.00 0.000.00 0.00 0.00 3.0% 2.90 3.20 3.08 3.06 0.15 1.0% 3.60 3.60 3.90 3.700.17 0.3% 2.90 3.60 3.56 3.35 0.39 D (μg) 32 0.00 0.00 0.00 0.00 0.00 160.00 0.00 0.00 0.00 0.00 8.0 0.00 0.00 0.00 0.00 0.00 4.0 1.61 2.30 0.001.31 1.18 2.0 2.30 0.00 2.78 1.69 1.49 1.0 4.72 2.60 2.30 3.21 1.32 0.53.90 2.90 3.64 3.48 0.52

Log Reductions are presented in Table 6

TABLE 6 Log Reductions Log % Reduction Comp. Log R T-test S/NS A Vs. B30.0% 3.70 0.00 S 10.0% 3.70 0.00 S  3.0% 3.66 0.00 S  1.0% 2.25 0.02 S 0.3% 0.98 0.03 S A Vs. C 30.0% 3.70 0.00 S 10.0% 3.70 0.00 S  3.0% 0.600.00 S  1.0% 0.00 0.50 NS  0.3% 0.45 0.07 NS GC Vs. D 32 4.59 0.00 S 164.59 0.00 S 8.0 4.59 0.00 S 4.0 3.29 0.00 S 2.0 2.90 0.00 S 1.0 1.380.02 S 0.5 1.11 0.00 S

MBC and MBEC Visual Reading data is presented in Table 7

TABLE 7 MBC and MBEC Visual Reading data 1 2 3 4 5 6 7 8 9 10 11 12 MBECA + + + − − − − − − − − − B + + + − − − − − − − − − C + + + − − − + + +− + − D + + + − − − + + + + + + E + + + + + + + + + + + + F − − − − −− + + + + + + G + + + + + + − − − + + + H − − − − − − + + + + + + MBCA + + + − − − − − − − − − B + + + − − − − − − − − − C + + + − − − − − −− − − D + + + − − − − − − − + + E + + + − − − − − − − + + F − − − − − −− − − + + + G + + + + + + − − − + + + H − − + − − − + + + + + +

Conclusion: The log reduction data indicated that the test article (TCPgranules coated with a matrix composition according to embodiments ofthe invention) managed to kill a preformed biofilm at a minimumconcentration of 3.0% and was effective even at 1.0% (>99% kill). Incontrast, the non-formulated doxycycline with β-TCP was effective atconcentrations of 10% or above.

Example 6—Inhibition of Biofilm Formation in the Presence in thePresence of TCP Particles Coated with a Matrix Composition According toSome Embodiments of the Invention

The effectiveness of tri-calcium phosphate granules coated with a matrixcomposition according to embodiments of the invention in inhibitingbiofilm formation was evaluated by calculating the bacterial logreduction values using the MBEC™ (Minimum Biofilm EradicationConcentration) Physiology and Genetics Assay (The system is describedabove in EXAMPLE 5).

Culture/Inoculum preparation followed the procedure described above inExample 5.

Preparation of the Challenge Plate:

TABLE 8 Staphylococcus aureus A SC-A SC-A SC-A B1 B1 B1 A1 A1 A1 B SC-BSC-B SC-B B2 B2 B2 A2 A2 A2 C N:50 N:50 N:50 B3 B3 B3 A3 A3 A3 D N N NB4 B4 B4 A4 A4 A4 E B5 B5 B5 A5 A5 A5 F G H BGCh BGCh BGCh Challengeplate design: SC wells are sterility controls for each experiment. GC isthe growth control. BGCh is the biofilm Growth Check. N wells are theneutralizer toxicity controls. N:50 wells are the efficacy controls.

Using a sterile 96-well microtitre plate the following was doneaseptically to set up the above challenge plates: Efficacy control: 150μL of the neutralizer was added to 672 μg of the doxycycline in the N:50 wells (final concentration of Doxycycline in D/E was 4.48 mg/mL).

Neutralizer toxicity control: 150 μL of the neutralizer was added to Nwells.

Biocide sterility control: 60 mg of the test-article were added to SCwells.

60 mg of each of TCP and test-article were added as in the layout ofTable 8 in columns 1-9 (n=3).

150 μL of the inoculated media were added to each well of the biofilmformation/challenge 96 well plate except for the sterility controls.

Antimicrobial Challenge for Biofilm Formation Inhibition:

The lid was transferred to the challenge plate and incubated on a rotaryshaker at 110 rpm at 35±2° C. for 24±2 hours.

Planktonic cells were rinsed from the biofilm that have formed on thelid of the MBEC device by dipping the lid into a rinse plate (200 μL ofsaline per well) for 30 seconds. After the specified contact time, theMBEC™ lid was transferred to the neutralizer plate (200 μL ofneutralizer per well).

The plate was placed in the sonicator and sonicated for 30 minutes todislodge surviving biofilm.

Determination of planktonic MBC and LOG₁₀ Reduction were done asdescribed above in Example 5.

Average LOG₁₀ recovery is summarized in Table 9 below.

TABLE 9 Average LOG₁₀ recovery 1 2 3 Average StDev A 30.0% 4.60 5.384.90 4.96 0.39 10.0% 5.30 5.56 5.45 5.43 0.13 3.0% 4.90 5.30 5.08 5.090.20 1.0% 5.38 5.51 5.60 5.50 0.11 0.3% 5.60 5.20 5.60 5.47 0.23 B 30.0%0.00 0.00 0.00 0.00 0.00 10.0% 0.00 0.00 0.00 0.00 0.00 3.0% 0.00 0.000.00 0.00 0.00 1.0% 0.00 0.00 0.00 0.00 0.00 0.3% 0.00 0.00 0.00 0.000.00

Log Reductions are Presented in Table 10

TABLE 10 LOG₁₀ reduction % Log Reduction Comp. LogR Ttest S/NS A Vs. B30.0% 4.96 0.00 S 10.0% 5.43 0.00 S  3.0% 5.09 0.00 S  1.0% 5.50 0.00 S 0.3% 5.47 0.00 S

MBC and MBEC Visual Reading Data is Presented in Table 11:

TABLE 11 MBC and MBEC Visual Reading data 1 2 3 4 5 6 7 8 9 MBC A − − −− − − + + + B − − − − − − + + + C − − − − − − + + + D + + + − − − + + +E + + + − − − + + + F G H MBEC A − − − − − − + + + B − − − − − − + + + C− − − − − − + + + D + + + − − − + + + E + + + − − − + + + F G H + + +

Conclusions: The A control compound (TCP only) had good recovery andgrowth over the duration of the challenge and at all testedconcentrations of TCP.

The B Test compound completely killed the bacteria that was inoculatedinto the test wells at every concentration tested. The MBC dataindicates that all the cells were killed and not simply inhibited at thetested concentrations.

Example 7—Pre-Clinical Testing of TCP Particles Coated/Impregnated witha Matrix Composition According to Embodiments of the Present Inventionfor the Treatment of Sternal Surgical Site Infection

The objective of this study is to assess the efficacy of tri-calciumphosphate granules (˜100 μm) coated with a matrix composition comprisingdoxycycline according to some embodiments of the invention (“Testarticle”) in reducing bacterial proliferation following induction of asurgical site infection (SSI) model attained by sternal implantation ofthe Test article combined with Staphylococcus aureus (ATCC 25923) in NewZealand White rabbits. The preparation of the “test article” isdescribed in Example 1.

DESCRIPTION

A sternum defect in half sternum depth is performed on New Zealand Whiterabbits. 12 Female New Zealand White rabbits are randomly divided intotwo equal groups of 6 animals. They underwent median sternotomy with theapplication of either a “control article” (uncoated TCP) or “testarticle” (TCP particles coated/impregnated with matrix compositionprepared as described in Example 1) mixed with a defined calibratedbacterial inoculum dose and are placed in the gap formed (e.g. sternumdefect).

Rabbits are anesthetized using ketamine (30 mg/kg), xylazine (5 mg/kg)and atropine (1 to 3 mg/kg) intramusculary and maintained on isofluraneafter intubation.

The sternotomy is performed using standard aseptic techniques. A sternumdefect in half sternum depth is performed. Equal amounts of controlarticle or test articles mixed separately with bacterial inoculum areapplied to cover the cut bone surface, and the time to hemostasis isrecorded. The sternum is surgically closed (sternal halves are securedwith monofilament suture, and incision is closed in layers). Dailyobservations are performed for general health. Animals are sacrificedafter 6 weeks. Each sternum is harvested for radiographic, histologic,hematologic and mechanical analysis to assess sternal healing.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the invention that others can, by applyingcurrent knowledge, readily modify and/or adapt for various applicationssuch specific embodiments without undue experimentation and withoutdeparting from the generic concept, and, therefore, such adaptations andmodifications should and are intended to be comprehended within themeaning and range of equivalents of the disclosed embodiments. It is tobe understood that the phraseology or terminology employed herein is forthe purpose of description and not of limitation. The means, materials,and steps for carrying out various disclosed functions may take avariety of alternative forms without departing from the invention.

1. A method for the treatment or prophylaxis of a surgical siteinfection associated with surgical operation comprising the step ofadministering to the surgical site a biodegradable substrate impregnatedor having its surface coated fully or partially with a matrixcomposition comprising (a) a biocompatible polymer, (b) a first lipidcomponent comprising at least one sterol which is non-covalentlyassociated with the biocompatible polymer, (c) a second lipid componentcomprising at least one phospholipid having fatty acid moieties of atleast 12 carbons; and (d) a pharmaceutically active agent.
 2. (canceled)3. The method according to claim 1, wherein the surgical operation inselected from orthopedic surgical operations, spine surgical operations,surgical operations on a digestive system organ, cardiac procedures,hernia repair, vascular procedures, caesarian, prostatectomy, obstetricand gynecologic surgical operations, head and neck cancer surgery,transplantation surgeries, neurosurgery and plastic surgeries.
 4. Themethod according to claim 1, implemented in addition to standard of careprocedures for reduction in the inoculum of bacteria selected from thegroup consisting of appropriate surgical site preparation, systemicpreventive antibiotics, cell based therapy, and enhancement of the hostby perioperative supplemental oxygenation, maintenance of normothermiaand glycemic control.
 5. The method according to claim 1, wherein thebiodegradable substrate is selected from the group consisting of amineral substrate, a natural polymer material, a water soluble syntheticpolymer and a bioabsorbable hydrophobic material.
 6. The methodaccording to claim 5, wherein the biodegradable substrate is a mineralsubstrate selected from the group consisting of hydroxyapatite,fluorapatite, oxyapatite, wollastonite, apatite/wollastonite glassceramics, anorthite, calcium fluoride, calcium sulfate, calciumcarbonate, tetracalcium phosphate, α-tricalcium phosphate (α-TCP),β-tricalcium phosphate (β-TCP), amorphous calcium phosphate, dicalciumphosphate, agrellite, devitrite, canasite, phlogopite, monetite,brushite, octocalcium phosphate, whitlockite, cordierite, berlinite,combeite, phosphoric acid crystals, disodium hydrogen phosphate, andother phosphate salt-based bioceramics.
 7. The method according to claim5, wherein the biodegradable substrate is a natural polymer materialselected from the group consisting of gelatin, hyaluronic acid,hyaluronic acid derivatives, such as, a polyionic complex of hyaluronicacid, triethanolamine alginate, casein, keratin, myosin and/or fibroin,collagen, collagen derivatives, such as, succinylated collagen ormethylated collagen, chondrotin sulfate, chitosan, chitosan derivatives,such as, methylpyrrolidone-chitosan, polyaminogalactosamine.
 8. Themethod of claim 5, the substrate is a water soluble synthetic polymer.9. The method of claim 8, wherein the substrate is poly vinyl alcohol(PVA).
 10. The method according to claim 1, wherein the biodegradablesubstrate consists of particles having an average particle size of lessthan about 200 microns (μm). 11-13. (canceled)
 14. The method accordingto any claim 10 wherein a majority of the particles are spherical and/orspheroidal.
 15. The method according to claim 1, wherein the matrixcomposition comprises a phospholipid selected from a phosphatidylcholineor a combination of phosphatidylcholines having fatty acid moietieshaving at least 12 carbons.
 16. The method according to claim 15,wherein said phospholipid is a phosphatidylcholine or a combination ofphosphatidylcholines having fatty acid moieties having 14-18 carbons.17. The method according to claim 1 wherein the biocompatible polymer inthe matrix composition, is a biodegradable polyester selected from thegroup consisting of PLA (polylactic acid), PGA (poly glycolic acid) andPLGA (Poly (lactic co glycolic acid).
 18. The method according to claim1, wherein the biocompatible polymer in the matrix composition is polyethylene glycol (PEG).
 19. The method according to claim 1, wherein thepharmaceutically active agent is selected from the group consisting ofan antibiotic agent, an antiseptic agent, an anti-inflammatory agent,anti-fungal agent and any combination thereof. 20-21. (canceled)
 22. Themethod according to claim 19, wherein the antibiotic agent is selectedfrom the group consisting of penicillin antibiotics, cephem antibiotics,macrolide antibiotics, tetracycline antibiotics, fosfomycin antibiotics,aminoglycoside antibiotics, and new quinolone antibiotics
 23. The methodaccording to claim 1, wherein the sterol in the matrix composition is acholesterol.
 24. (canceled)
 25. The method according to claim 1 whereinthe coated substrate comprises between about 60-90% (w/w) of substrateand 10-40% (w/w) of the matrix composition.
 26. (canceled)
 27. Themethod according to claim 1, wherein said matrix composition issubstantially free of water.
 28. The method according to claim 1,wherein when the coated substrate is maintained in an aqueousenvironment, the matrix composition provides sustained release of saidpharmaceutically active agent, wherein at least 30% of saidpharmaceutical active agent is released from the composition atzero-order kinetics.
 29. A method for the treatment or prophylaxis of asurgical site infection associated with surgical operation comprisingthe step of applying to the surgical site a biodegradable substrateimpregnated or having its surface coated fully or partially with amatrix composition comprises: (a) 15-25% (w/w) poly (lactic-co-glycolicacid) (PLGA) (b) 5-15% (w/w) of cholesterol; (c) 50-70% (w/w) of amixture of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), wherein the ratio ofDPPC to DSPC is between 5:1 and 2:1 and (d) 7-12% (w/w) of doxycyclineor doxycycline hyclate, wherein the substrate constitutes between about80-90% (w/w) and the matrix composition constitutes about 10-20% (w/w)of the total weight of the coated substrate. 30-53. (canceled)
 54. Themethod of claim 1, wherein infection is caused by hospital acquiredbacteria.
 55. The method of claim 1, wherein infection is caused byMethicillin-resistant S. aureus (MRSA).
 56. The method according toclaim 22, wherein the antibiotic agent is a tetracycline antibioticselected from doxycycline and doxycycline hyclate.
 57. The methodaccording to claim 1, wherein the coated biodegradable substrate isformulated as a paste prior to its application.
 58. A method for thetreatment or prophylaxis of a sternal wound infection associated withcardiac surgery procedure, comprising the step of applying to thesternal halves and/or surrounding soft tissue, a biodegradable substrateimpregnated or having its surface coated fully or partially with amatrix composition comprising (a) a biocompatible polymer, (b) a firstlipid component comprising at least one sterol, (c) a second lipidcomponent comprising at least one phospholipid having fatty acidmoieties of at least 12 carbons; and (d) a pharmaceutically active agentselected from the group consisting of an antibiotic agent, antisepticagent, an anti-inflammatory agent, anti-fungal agent and any combinationthereof.